Using SqlDataReader.GetString When Value In Database Might Be A NULL
Jun 8, 2007
I am currently using the following code to populate fields in a form
EditUserNotes.Text = EditUserReader.GetString(2);
which works just fine (the datatype in the database is 'text') as long as the data stored in the database is not null. If the data is null, I get the error: Data is Null. This method or property cannot be called on Null values. which is really annoying as there are times when the data stored in the database is legitimately NULL
I can use the following code to fix the problem, but it seems less elegant
EditUserNotes.Text = EditUserReader.GetValue(2).ToString()
is there really a difference between the GetString and the GetValue(x).ToString() methods or are they interchangeable?
View 3 Replies
ADVERTISEMENT
Nov 3, 2004
In my database I have this code:
Do While sqlDataReader.Read()
lblTitle.InnerText = sqlDataReader.GetString(2)
Loop
And this will get my sql's 3rd column ( its #2 because its 0-indexed ), but I am throwing this error when I try to print this sqlDataReader.GetString(2) if this particular value is a int. How do I cast it to a String.
I have already done these two things:
sqlDataReader.GetString(2).ToString()
&
CStr(sqlDataReader.GetString(2))
????
j
View 2 Replies
View Related
Jun 3, 2008
Hi gang,
When reading a record from my SQL database for display on a web form, I am checking for null before I assign the value to a TextBox on the form. Here is an example:
// normal database setup code hereSqlDataReader rdr = cmd.ExecuteReader();if (!Convert.IsDBNull(rdr["FirstName"])){ txtFirstName.Text = (string)rdr["FirstName"];}// code here for other record fields
Is this the correct way to do this? Is there a simpler way to do this? I am writing a bunch of database code and I want to do it right...
Thanks,Kevin
View 5 Replies
View Related
Mar 3, 2008
Hi.
I'm trying to read data from a database. This is my code:
++++++++++++++++++++++++++++++++++++++++++++++++++++++++
connection.Open();SqlCommand cmd = new SqlCommand(sql, connection);
myReader = cmd.ExecuteReader();if (myReader.Read())
{
name1TextBox.Text = myReader.GetString(1);
addr1TextBox.Text = myReader.GetString(2);
code1TextBox.Text = myReader.GetString(5);
tel1TextBox.Text = myReader.GetString(6);
fax1TextBox.Text = myReader.GetString(7);
:
:
++++++++++++++++++++++++++++++++++++++++++++++++++++++++
The above code works fine until one of the GetString calls trys to return NULL (in this case myReader.GetString(5)).
In other words, this code will run through about 30 rows of data until it runs in to a NULL entry for one of the columns.
At that stage it's too late. I'm not allowed call GetString( ) on a NULL value.
Is there anyway I can test the column entry before calling GetString( ).
Regards (& thanks in advance)
Garrett
View 4 Replies
View Related
Feb 11, 2004
how can i add two columns in each row (both strings) in a table only using getstring?
i'm getting an error from this statement... thanks
dim row as string
while dr.read()
problem with this statment
------->> row = dr.getstring(1) + dr.getstring(2)
end while
View 6 Replies
View Related
Apr 1, 2008
I used SQLDataReader to assign a OrderID to a text box.
OrderID is varchar type. I got cast error. How to fix it?
Me.txtOrderID.Text = myDataReader.GetString("OrderID")
View 6 Replies
View Related
Jun 28, 2004
I would drop and add the table but the data can't be deleted. So if anyone could help with the statement it would be greatly appreciated. Thanks
View 7 Replies
View Related
Oct 27, 2015
We have a case where in we should show date based on conditions for e.g if we had a column defined as
col varchar(10) then we would show col as 'NULL' for some condition and actual value when no condition
Normaly date values are stored here e.g under col 20150901 .
Case
when col>'20150901' then 'NULL'
else col
end as Derivedcol
Note this is an extract process and we are presenting data by pumping the data in a table .
Now there is another similar column -colz varchar(10) which stores date but doesnt have case condition so whenever date has no value its shows null which is database null.
So whats the difference between database null and string null ?
How can we show database null for the case condition instead of string "null"?
View 10 Replies
View Related
Sep 20, 2006
Hey. I need to substitute a value from a table if the input var is null. This is fine if the value coming from table is not null. But, it the table value is also null, it doesn't work. The problem I'm getting is in the isnull line which is in Dark green color because @inFileVersion is set to null explicitly and when the isnull function evaluates, value returned from DR.FileVersion is also null which is correct. I want the null=null to return true which is why i set ansi_nulls off. But it doesn't return anything. And the select statement should return something but in my case it returns null. If I comment the isnull statements in the where clause, everything works fine. Please tell me what am I doing wrong. Is it possible to do this without setting the ansi_nulls to off??? Thank you
set ansi_nulls off
go
declare
@inFileName VARCHAR (100),
@inFileSize INT,
@Id int,
@inlanguageid INT,
@inFileVersion VARCHAR (100),
@ExeState int
set @inFileName = 'A0006337.EXE'
set @inFileSize = 28796
set @Id= 1
set @inlanguageid =null
set @inFileVersion =NULL
set @ExeState =0
select Dr.StateID from table1 dR
where
DR.[FileName] = @inFileName
AND DR.FileSize =@inFileSize
AND DR.FileVersion = isnull(@inFileVersion,DR.FileVersion)
AND DR.languageid = isnull(@inlanguageid,null)
AND DR.[ID]= @ID
)
go
set ansi_nulls on
View 3 Replies
View Related
Nov 29, 2007
Hi..
Every time I want to read any record from data base I read it in dataset for example:SqlConnection con = new SqlConnection(@"Data Source=localhost ;Initial Catalog=university ;Integrated Security=True");
SqlCommand cmd = new SqlCommand("select [User_AuthorityID] from users where [UserID]='" + TextBox1.Text + "' and [UserPassword]='" + TextBox2.Text + "' ", con);SqlDataAdapter adp = new SqlDataAdapter();
adp.SelectCommand = cmd;DataSet ds = new DataSet();
adp.Fill(ds, "UserID");foreach (DataRow dr in ds.Tables["UserID"].Rows)
{
user_type = dr[0].ToString();
Session.Add("User_AuthorityID", user_type);
.........
Is there easier way to read data from data base?
How I can use SqlDataReader to do that?
Thanks..
View 4 Replies
View Related
Jun 1, 2008
Hey All,
I have come across a situation with two tables, they are dynamic and the user can add and edit values in the tables so I need to build a dynamic display control. It is all based around an FAQ system I have built. The user can create new FAQ categories (that is one table) then create a new FAQ Question & Answer (that is the second table). The tables are linked by the category id. So now I am trying to display the FAQ section like so.
CATEGORY NAME
QuestionAnswerQuestionAnswerCATEGORY NAME
QuestionAnswerQuestionAnswerCATEGORY NAME
QuestionAnswerQuestionAnswer
So my idea was to run a loop within a loop. First loop the category name, then within the category name, loop a second time to grab all of the questions & answers within the category id captured from the first loops sql select statement, then proceed to loop the category name again and of course repeat the process until all loops are completed. However I am getting, and I kinda figured I would get an error about my SQLDataReader. Bellow is my code maybe some type of edit or different recommendation is needed. Any help will do, thanks!Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
'--- Database Connection ---Dim sConnStr As String = ConfigurationManager.ConnectionStrings("ConnectionString").ConnectionString
Dim cnBKPost As New SqlConnection(sConnStr)
'--- End DB Connection ----
'----- FAQ's -------
Dim sql As String = "SELECT category_id, category_name FROM faq_category ORDER BY category_name DESC"Dim cmd As New SqlCommand(sql, cnBKPost)
cnBKPost.Open()Dim reader As SqlDataReader = cmd.ExecuteReader()
Dim str As New StringBuilder()
Dim catid As IntegerDo While reader.Read()
'--- Category Titles ----catid = reader("category_id")
str.Append("<h2>" & reader("category_name") & "</h2>")
'--- End Category Title ---
'--- Get FAQ's In Category ---
Dim sqlcat As String = "SELECT faq_question, faq_answer FROM tbl_faq WHERE faq_category = '" & catid & "'"Dim cmdcat As New SqlCommand(sqlcat, cnBKPost)
Dim readerfaq As SqlDataReader = cmdcat.ExecuteReader()Do While readerfaq.Read()
str.Append("<p><font style='font-size:12pt;font-color:#daa520;>'" & reader("faq_question") & "</font><br />")str.Append(reader("faq_answer") & "</p>")
str.Append("<br /><br /><br />")
Loop
readerfaq.Close()
'--- End Get FAQ's in Category ---
Loop
reader.Close()
cnBKPost.Close()Me.Literal1.Text = str.ToString()
End Sub
End Class
View 2 Replies
View Related
Jun 25, 2004
i'm using c# and SqlDataReader to simply retrieve data from one column of a database. problem is it's an integer i'm trying to retrieve, and so i'm trying to put it into an int variable, and i get the error "CS0029: Cannot implicitly convert type 'object' to 'int'" . i've looked for an answer for about an hour and every example for the SqlDataReader that i can find deals with strings only or the examples are too complex for me to understand.
there must be an easy way to retrieve this data and put it into an integer! help...
my line of code that creates the error:
int intGuestNum = dtrSelectTotalSessions["online_numSessions"];
View 5 Replies
View Related
Aug 29, 2006
Hi, from what I can find, there isn't a way to get the number of rows returned from a SQLDataReader command. Is this correct? If so, is there a way around this? My SQLDataReader command is as follows:Dim commandInd As New System.Data.OleDb.OleDbDataAdapter(strQueryCombined, connInd)Dim commandSQL As New SqlCommand("GetAssetList2", connStringSQL)Dim resultDS As New Data.DataSet()'// Fill the dataset with valuescommandInd.Fill(resultDS)'// Get the XML values of the dataset to send to SQL server and run a new queryDim strXML As String = resultDS.GetXml()Dim xmlFileList As SqlParameterDim strContainsClause As SqlParameter'// Create and execute the search against SQL ServerconnStringSQL.Open()commandSQL.CommandType = Data.CommandType.StoredProcedurecommandSQL.Parameters.Add("@xmlFileList", Data.SqlDbType.VarChar, 1000).Value = strXMLcommandSQL.Parameters.Add("@strContainsClause", Data.SqlDbType.VarChar, 1000).Value = strContainsConstructDim sqlReaderSource As SqlDataReader = commandSQL.ExecuteReader()results.DataSource = sqlReaderSourceresults.DataBind()connStringSQL.Close()And the stored procedure is such:DROP PROC dbo.GetAssetList2;GOCREATE PROC dbo.GetAssetList2(@xmlFileList varchar(1000),@strContainsClause varchar(1000))ASBEGINSET NOCOUNT ONDECLARE @intDocHandle intEXEC sp_xml_preparedocument @intDocHandle OUTPUT, @xmlFileListSELECT DISTINCTAssetsMaster.AssetMasterUID,SupportedFiles.AssetPath,FROM AssetsMaster, OPENXML (@intDocHandle, '/NewDataSet/Table',2) WITH (FILENAME varchar(256)) AS x,SupportedFilesWHEREAssetsMaster.AssetFileName = x.FILENAMEAND AssetsMaster.Extension = SupportedFiles.Extension UNIONSELECT DISTINCTAssetsMaster.AssetMasterUID,SupportedFiles.AssetPath,FROM AssetsMaster, OPENXML (@intDocHandle, '/NewDataSet/Table',2) WITH (FILENAME varchar(256)) AS x,SupportedFilesWHEREAssetsMaster.AssetFileName <> x.FILENAMEAND CONTAINS ((Description, Keywords), @strContainsClause)AND AssetsMaster.Extension = SupportedFiles.ExtensionORDER BY AssetsMaster.Downloads DESCEXEC sp_xml_removedocument @intDocHandle ENDGOHow can I access the number of rows returned by this stored procedure?Thanks,James
View 3 Replies
View Related
Feb 16, 2007
How do I tell when there is no more data to read in a SQLDataReader?
For example, I have an open datareader that I pass into a function that MIGHT still have a valid row in it when it returns from the function. How do I tell? I can't do a read() because then that current record will go away. I need to be able to tell if there is a current record without doing another read.
TIA,
View 4 Replies
View Related
Jun 18, 2007
Say I have this SQL query running into an SqlDataReader select TaskName, TaskDescription from tblTasks where TaskID = 5 There are two different ways to get the data out of the reader (maybe more) TaskName.Text = Reader.GetString(0);andTaskName.Text = Reader.GetString(Reader.GetOrdinal("TaskName")); My question is, is there a major difference in terms of efficiency between these two? The second one is definitely more robuts (in a situation where you are calling a stored procedure, and the stored procedure might change, etc) but the first one has fewer operations. Is the increase in robustness of the second one worth the potential performance hit, if any? Thank you, -Madrak
View 2 Replies
View Related
Jul 23, 2007
May I know what is the purpose of having SqlDataReader in Example A? I can see the same output when I tried out both. Should I use Example A or Example B? Currently, I'm using Example B since it is lesser code.Example A Dim objDR As SqlDataReader 'Create Data Reader
LoginConn.Open()
strSQL = "SELECT CountryID, CountryName FROM Country ORDER BY CountryName "
cmd = New SqlCommand(strSQL, LoginConn) objDR = cmd.ExecuteReader() 'Populate the DataReader ddlNationality.DataSource = objDR ddlNationality.DataBind() ddlNationality.SelectedValue = dvUserProfile.Item(0)("Nationality")LoginConn.Close() Example BLoginConn.Open() strSQL = "SELECT CountryID, CountryName FROM Country ORDER BY CountryName " cmd = New SqlCommand(strSQL, LoginConn) ddlNationality.DataSource = cmd.ExecuteReader() 'Populate the DataReader ddlNationality.DataBind() ddlNationality.SelectedValue = dvUserProfile.Item(0)("Nationality")LoginConn.Close()
View 2 Replies
View Related
Dec 31, 2007
Hello every one and happy new year...
i have a problem with SqlDataReader used in asp.net application:
I defined a public object of SqlDataReader and assigned it the resultset of a query,
well, this happened ,lets say in page 1# but whan i want to use this datareader in another page
it keeps telling my that the reader is closed so i can't abstract information from, regarding that i used it's methods such "Read()" and "NextResult()"
but there is no use, what should i do, help me please !!!!!?
View 1 Replies
View Related
Jan 4, 2008
Hello im fairly new to ASP.Net and have a problem with an Intranet Page I am creating. In this part of the page I want to retrive a value from an SQL Table based on criteria and then store it as a variable to be used elsewhere on my page. I have tried using the SQL Data reader to retrive the value but somewhere in my code I am going wrong. Can anyone advise me on this please? See code below
My Visual Studio debugger has point out that there is a problem with my r = cmd.ExecuteReader() line
Oh and the connection to my SQL database is opened further up the page from this code.
Dim strSQL As String = "SELECT top 1 OrderID FROM tblStationeryOrder WHERE ORDERMADEBY = '" & lstUsers.SelectedValue & "' ORDER BY OrderID DESC"Dim cmd As New System.Data.SqlClient.SqlCommand
cmd.CommandText = strSQLDim r As System.Data.SqlClient.SqlDataReader
r = cmd.ExecuteReader()Do While r.Read()
Dim OrderID As Integer = r!OrderID
Exit Do
View 4 Replies
View Related
Apr 25, 2008
I found this tutorial at C# Station called "Reading Data with the SqlDataReader".
In my code behind file I followed what I think the tutorial was telling me to do but I keep getting a syntax error near '='
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Data.SqlClient.SqlException: Line 1: Incorrect syntax near '='. (Line 45: rdr = cmd.ExecuteReader();)
Heres my code:
protected void Page_Load(object sender, EventArgs e) { this.lblDate.Text = DateTime.Today.ToString("d"); string username; username = Convert.ToString(Session["usr"]); SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["csSecurity"].ConnectionString); SqlDataReader rdr = null; SqlCommand cmd = new SqlCommand("SELECT PROG_OFF FROM Logon_Table WHERE usr = " + username, conn); try { conn.Open(); rdr = cmd.ExecuteReader(); }
Any suggestions here would be great. Any links to tutorials you know of would be helpful also.
Thanks
View 2 Replies
View Related
May 18, 2008
good afternoon everybody
this is my code: and their is an error ,,really dunno where and why coz it seems logical to me :)Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
If RadioButton1.Checked = True Then
Dim admin As Stringadmin = "SELECT * from ADMINISTRATOR where UserName='" & TextBox1.Text & "' and UserPassword='" & TextBox2.Text & "'"
Dim sConnect As String = "Data Source=.SQLEXPRESS;AttachDbFilename=|DataDirectory|Database.mdf;Integrated Security=True;User Instance=True"Dim cnt As New SqlConnection
cnt.ConnectionString = sConnect
cnt.Open()Dim com As New SqlCommand
com.Connection = cnt
com.CommandText = adminerror!!>>>>Dim rd As SqlDataReader
rd = com.ExecuteReader
If rd.Read ThenSession("admn") = rd("UserName")Session("id") = rd("UserID")
rd.Close()
cnt.Close()Response.Redirect("~/adminpage.aspx")
ElseSession("admn") = 0
Label3.Visible = True
rd.Close()
cnt.Close()
End If
Else
Dim instrct As Stringinstrct = "SELECT * from instructor where name='" & TextBox1.Text & "' and passs='" & TextBox2.Text & "'"
Dim sConnect As String = "Data Source=.SQLEXPRESS;AttachDbFilename=|DataDirectory|Database.mdf;Integrated Security=True;User Instance=True"Dim con As New SqlConnection
con.ConnectionString = sConnect
con.Open()Dim com As New SqlCommand
com.Connection = con
com.CommandText = instrctDim r As SqlDataReader
r = com.ExecuteReader
If r.Read ThenSession("inst") = r("inst_name")
r.Close()
con.Close()Response.Redirect("~/instructorpage.aspx?id=" & Session("inst"))
ElseSession("inst") = 0
Label3.Visible = True
r.Close()
con.Close()
End If
End If
End Sub
-----------------
this is the error line:
The data types text and varchar are incompatible in the equal to operator.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Data.SqlClient.SqlException: The data types text and varchar are incompatible in the equal to operator....
so,,,any suggestions?
View 2 Replies
View Related
Jun 7, 2008
I have an sp, which has 2 select statements, so iam using a sqldatareader and binding the data to a dropdown.
the first binding is fine, but when i say dataReader.NextResult(), It is null.It says the reader is closed. Can any one tell a work around for this.
thanx in advance,
Anil Kumar.
View 6 Replies
View Related
Jun 10, 2008
see ths code. please
== DAL ==
public static SqlDataReader ExecuteReader(SqlParameter param, string sp) { using (conn = new SqlConnection(connectString)) { SqlDataReader sdr = null; try { conn.Open();
comm = new SqlCommand(); comm.CommandText = sp; comm.CommandType = CommandType.StoredProcedure; comm.Connection = conn; comm.Parameters.Add(param); sdr = comm.ExecuteReader(CommandBehavior.CloseConnection); } catch(SqlException e) { WriteToLog(e.Message); } return sdr; } }
and, call above ExecuteReader() flowing this,
== BL ==
public UserEntity GetUserInformation(string UID, string sp) { UserEntity ue = new UserEntity();
SqlParameter userUID = new SqlParameter("@USR_ID", SqlDbType.VarChar, 20); userUID.Value = UID;
using (SqlDataReader sdr = DbHelper.ExecuteReader(userUID, "SP_GETUSERINFORMATION")) { if (sdr != null) { while (sdr.Read()) { ue.UserId = sdr["lecture_usr_id"].ToString(); ue.UserName = sdr["lecture_usr_realname"].ToString(); ue.Email = sdr["lecture_usr_email"].ToString(); ue.Phone = sdr["lecture_usr_phone"].ToString(); ue.Lastlogin = (DateTime)sdr["lecture_usr_lastlogin"]; ue.SignDate = (DateTime)sdr["lecture_usr_signdate"]; } } return ue; } }
error message is,
Invalid attempt to call Read when reader is closed.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.InvalidOperationException: Invalid attempt to call Read when reader is closed.Source Error:
Line 77: if (sdr != null)
Line 78: {
Line 79: while (sdr.Read())
Line 80: {
Line 81: ue.UserId = sdr["lecture_usr_id"].ToString();Source File: C:Users
aphyrDocumentsVisual Studio 2008ProjectslectureBusinessLogicUserManager.cs Line: 77
I can't understand!!! I try to debuging!!! but, I don't know.
please help me!
View 2 Replies
View Related
Jun 14, 2008
suppose I have a data reader which is returned by excuting a command "SELECT [xxx], [yyy], FROM [zzz]" , then I reads the data as normal. while I am reading , there is another thread that excute an insert command to that table , does this insertion effect the order of data that I am reading?
View 5 Replies
View Related
Apr 17, 2005
I have an SP that returns a result set that contains a tinyint. My problem is that, when I try and access this value using GetInt16 (or 32), I get an error saying that "Specified cast is not valid". TinyInt is 1 byte, or 8 bits. GetInt16 'Gets the value of the specified column as a 16-bit unsigned integer'. I am assuming that this is the root cause of my problem. But, there doesn't seem to be a GetInt8 ?! Any ideas?
Thanks, Martin
View 1 Replies
View Related
Jan 29, 2006
hi..i am kind of new to asp.net n having trouble with the SqlException error message.. n this code works as 1st page pass the id to second page and the second page took the id to execute the query..i dun know the wer the error occurs..can give a help..Thanks.
private void Page_Load(object sender, System.EventArgs e)
{
SqlConnection connection = null;
SqlCommand command = null;
string sqlConnection = null;
string sql = null;
string ab = null;
sqlConnection = ConfigurationSettings.AppSettings["MSQLConnectionString"];
connection = new SqlConnection(sqlConnection);
if (!Page.IsPostBack)
{
try
{
if (Request.QueryString["categoryID"] == null)
{
}
else
{
ab= Request.QueryString["categoryID"].ToString(); //getting the id from page that pass this values
sql = "Select groupname, categoryid, description from groups where groups.categoryid=?"; // can this query execute?
command = new SqlCommand(sql, connection);
connection.Open();
command.Parameters.Add(new SqlParameter("categoryid", ab));
reader = command.ExecuteReader(); // error on here "SqlException"
while (reader.Read())
{
group.InnerText = reader["groupname"].ToString();
desc.InnerText = reader["description"].ToString();
}
}
}
finally
{
if (reader != null)
{
reader.Close();
}
if (connection != null)
{
connection.Close();
}
}
}
View 1 Replies
View Related
May 18, 2006
I am considering not to allow null values in the database.
what are pros and cons ?
View 3 Replies
View Related
Feb 13, 2007
My query is as follows:Dim CurrentDate As DateCurrentDate = "09/02/2007" MyCommand = New SqlCommand("SELECT RegisterID FROM Registers WHERE RegisterDate = @RegisterDate AND IsMorningRegister = 1", MyConn)MyCommand.Parameters.Add("@RegisterDate", Data.SqlDbType.DateTime)MyCommand.Parameters("@RegisterDate").Value = CurrentDate My DB table is called RegisterDate and is of type DateTime. The record that should be matched is: Register ID: 13 RegisterDate: 09/02/2007 09:00:00IsMorningRegister: TrueIsAfternoonRegister: False But no records are returned. Any idea why?
View 4 Replies
View Related
Feb 28, 2007
I am trying to access data using this code:
SqlCommand myCommand = new SqlCommand("myStoredProcedure", myConnection);
myCommand.CommandType = CommandType.StoredProcedure;
myCommand.Parameters.Add(new SqlParameter("@myID", SqlDbType.Int));
myCommand.Parameters["@myID"].Value = myIDValue;
myConnection.Open();
myDataReader = myCommand.ExecuteReader();
myTextBox.Text = myDataReader["myColumn"].ToString();
myDataReader.Close();
myConnection.Close();
I get "data reader has no data" error.
A problem with the parameter?
The stored procedure returns a row when executed from the database explorer.
I have used datasets and table adapters up to now as in the data access tutorial on this site
Any Ideas?
Thanks
View 1 Replies
View Related
Mar 14, 2007
Hi,I use SqlDataReader to read one row from database and than set some properties to values retrieved like this:string myString = myReader.GetValue(0) // this sets myString to first value in a rowIf, however, I change order of columns returned by stored procedure myString would be set to wrong value. Is there a way to do something like this: string myString = myReader.GetValue["ColumnName"];
View 7 Replies
View Related
Jun 20, 2007
Hello,
im using sqldatareader to read my data and whenever time i loop through the reader it starts from second row why is that?
here is my code:while (reader.Read()){hinfo.Name = reader["_name"].ToString();hi.Add(hinfo);}
i look at the database and i have two rows but its reading only the second row, skiping the first row
View 2 Replies
View Related
Aug 23, 2007
I am getting a random exception coming out of ADO.NET's SqlDataReader that I can't seem to track down for the life of me. I have put SQL Server and IIS under heavy load, with neither giving me the exceptions except occasionally (they come when there is no load as well). Web Site is built in VS2005 using .NET 2.0.
Basically, I have a web page that caches a few tables from a SQL database (about 10 tables are loaded into cache from this page) and the error can come from any of the tables while they are being read from the database randomly. I had assumed it was possible that a timeout was occuring while reading the data but from what the brief results google shows, there would be a different exception thrown it a timeout had occured.
Here is the exception that is showing up:
System.NullReferenceException: Object reference not set to an instance of an object. at System.Data.SqlClient.SqlDataReader.ReadColumnHeader(Int32 i) at System.Data.SqlClient.SqlDataReader.ReadColumn(Int32 i, Boolean setTimeout) at System.Data.SqlClient.SqlDataReader.GetValueInternal(Int32 i) at System.Data.SqlClient.SqlDataReader.GetValue(Int32 i) at Library.Data.DataProxy.ExecuteStoredProcedure(ArrayList& returnValues, TypeFactory factory)
I got the following exception once from the same section of code as well:
System.InvalidOperationException: Invalid attempt to FieldCount when reader is closed. at System.Data.SqlClient.SqlDataReader.get_FieldCount() at Library.Data.DataProxy.ExecuteStoredProcedure(ArrayList& returnValues, TypeFactory factory)
The code generating these errors is on line 29 below:
1 /// <summary>2 /// Executes a stored procedure that returns values3 /// </summary>4 /// <param name="returnValues">An arraylist of Types</param>5 /// <param name="factory">The Type specific factory</param>6 /// <returns>True if successful, false otherwise</returns>7 public bool ExecuteStoredProcedure(out ArrayList returnValues, TypeFactory factory)8 {9 bool bResult = true;10 SqlDataReader reader = null;11 12 returnValues = new ArrayList();13 MenseType nextType = null;14 15 try16 {17 // Open database connection18 OpenConnection();19 20 // execute SP21 reader = m_sqlCommand.ExecuteReader();22 23 while(reader.Read())24 {25 nextType = factory.CreateInstance();26 27 for(int i = 0; i < reader.FieldCount; i++)28 {29 object val = reader.GetValue(i);30 31 if(DBNull.Value == val)32 val = null;33 34 nextType.SetValue(reader.GetName(i), val);35 }36 37 returnValues.Add(nextType);38 39 } // while40 41 } // @ try42 catch(Exception ex)43 {44 returnValues = null;45 m_LastError = ex.ToString();46 bResult = false;47 48 #if(DEBUG)49 Library.IO.Logging.AddSQLMessage(ex);50 #endif51 52 } // @ catch53 finally54 {55 // close the reader if nessessary56 if (null != reader)57 reader.Close();58 59 // close db connection60 CloseConnection();61 62 } // @ finally63 64 return bResult;65 66 } // ExecuteStoredProcedure()
Any input would be greatly appreciated.
View 1 Replies
View Related
Oct 5, 2007
I have a SqlDataReader object that has some records:
1 hello12 hello23 hello3
Is there a fast/easy way to reorder them?
3 hello32 hello21 hello1
View 2 Replies
View Related
Dec 26, 2007
I have an SqlDataReader which loops through records returned from an SP, within that loop I would like to initiate another SP, but for some darn reason the following code won't work: // create SqlConnection object
string ConnectionString = ConfigurationManager.ConnectionStrings["aiv3cs"].ConnectionString;
SqlConnection myConnection = new SqlConnection(ConnectionString);
try
{
// Create a new XmlTextWriter instance
XmlTextWriter writer = new
XmlTextWriter(Server.MapPath("products.sitemap"), Encoding.UTF8);
writer.WriteStartDocument();
writer.WriteStartElement("siteMap");
writer.WriteAttributeString("xmlns", "http://schemas.microsoft.com/AspNet/siteMap-File-1.0");
// create the command
SqlCommand myCommand = new SqlCommand();
myCommand.Connection = myConnection;
// set up the command
myCommand.CommandText = "spGetMenuStructure";
myCommand.CommandType = CommandType.StoredProcedure;
// open the connection
myConnection.Open();
// run query
SqlDataReader myReader = myCommand.ExecuteReader();
bool HasSubElements = false;
SqlCommand myCommand2 = new SqlCommand();
SqlParameter myParameter1 = new SqlParameter();
SqlDataReader myReader2 = new SqlDataReader();
// parse the results
while (myReader.Read())
{
// create the command
myCommand2.Connection = myConnection;
// set up the command
myCommand2.CommandText = "spGetMenuSubElements";
myCommand2.CommandType = CommandType.StoredProcedure;
myParameter1.ParameterName = "@ContentID";
myParameter1.SqlDbType = SqlDbType.Int;
myParameter1.Value = Convert.ToString(myReader["ID"]);
myCommand2.Parameters.Add(myParameter1);
// run query
myReader2 = myCommand2.ExecuteReader();
while (myReader2.Read())
{
HasSubElements = true;
}
myReader2.Close();
if (Convert.ToString(myReader["HasPage"]) == "1")
{
writer.WriteStartElement("siteMapNode");
writer.WriteAttributeString("title", Convert.ToString(myReader["PageTitle"]));
writer.WriteAttributeString("description", Convert.ToString(myReader["PageTitle"]));
string PageURL = Convert.ToString(myReader["PageName"]) + "?ContentID=" + Convert.ToString(myReader["ID"]);
writer.WriteAttributeString("url", PageURL);
if (HasSubElements)
{
writer.WriteEndElement();
}
}
else
{
writer.WriteStartElement("siteMapNode");
writer.WriteAttributeString("title", Convert.ToString(myReader["PageTitle"]));
writer.WriteAttributeString("description", Convert.ToString(myReader["PageTitle"]));
}
HasSubElements = false;
}
myReader.Close();
// end the xml document and close
writer.WriteEndElement();
writer.WriteEndDocument();
writer.Close();
}
finally
{
myConnection.Close();
}I've gotten the following two errors:There is already an open DataReader associated with this Command which must be closed first.And a build error:Error29The type 'System.Data.SqlClient.SqlDataReader' has no constructors defined Any suggestions would be most appreciated.
View 4 Replies
View Related
