Does SQL Substitute Float = 0 With DBNull.Value?

Hi


I have only been coding in .Net for about six months, and am not sure if this is a C# problem or an SQL one. I use the Data Access Application Block in my program.





I have two optional fields on my form (RangeFrom and RangeTo). If the user chooses not to enter data into these textboxes(textbox = ""), an entry on the db is created with null values. It works.





But sometimes the user wants to enter 0 as either an upper or lower end of a range. This is where my problem comes in. My program saves 0 as null too.





In my program I do a test on the textboxes and populate two float values in a business object (objQuestion) accordingly, like this:








if (txtrangefrom.Text != "") {


objQuestion.RangeFrom=float.Parse(txtrangefrom.Text);


objQuestion.RangeTo=float.Parse(txtrangeto.Text);


}


else {


objQuestion.RangeFrom=Convert.ToSingle(null);


objQuestion.RangeTo=Convert.ToSingle(null);


}








And this is what my Business object look like. It sets up the parameters and calls the Data Access Application Block to create an entry in my table:








// fieldslist


float cvintRangeFrom;


float cvintRangeTo;





//properties


public float RangeFrom {


get {


return cvintRangeFrom;


}


set {


cvintRangeFrom = value;


}


}





public float RangeTo {


get {


return cvintRangeTo;


}


set {


cvintRangeTo = value;


}


}





// some code deleted for readability....





public int AddOption() {


string cvstrSpName = "addOption";


SqlParameter [] cvstrStoredParams = SqlHelperParameterCache.GetSpParameterSet(gcstrConnectionString, cvstrSpName, true);


//lines deleted for readability...


//check if the optional fields have a value associated with them. if not, assign dbnull.value.


cvstrStoredParams[4].Value=(cvintRangeFrom != Convert.ToSingle(null) ? cvintRangeFrom : (object)DBNull.Value);


cvstrStoredParams[5].Value=(cvintRangeTo != Convert.ToSingle(null) ? cvintRangeTo : (object)DBNull.Value);


//lines deleted for readability...


SqlHelper.ExecuteNonQuery(gcstrConnectionString, CommandType.StoredProcedure, cvstrSpName, cvstrStoredParams);


return(cvintOptionID = Convert.ToInt32(cvstrStoredParams[0].Value));


}








I use Convert.ToSingle when working with nulls (or possible nulls) because I get an error when I use float.parse for this.





The thing is, after this method AddOption has been executed, I test the value if the business object's rangefrom (that is where I entered 0) and display it on my form. I still shows a 0, but on my database table it is null!








objQuestion.AddOption();


//txtrangefrom.Text=""; on the next line I test the value in the business object...


txtrangefrom.Text=objQuestion.RangeFrom.ToString(); // and this displays 0!!!


//txtrangeto.Text="";


txtrangeto.Text=objQuestion.RangeTo.ToString();








So to me it seems the problem seems to be either the DAAB or on the SQL side, but hopefully somebody can prove me wrong! I was thinking that it could also be float.parse/Convert.ToSingle methods and have done various tests, but I am none the wiser...


Any help or ideas will be greatly appreciated...