Textbox Valiadation In SQLServer/C#2005

Hi, sorry if this is in the wrong forum

I’m hoping someone can help me with this problem. In theory it’s basic enough but I can’t get my head around it!!!!

I have a basic form that has a drop down list a text box. I’m selecting a static value from a list in the drop down list. Depending on this value I select I enter text into the textbox. What I can’t figure out is how to check/validate the value in the textbox against the value in the database.  I’m using a SqlDataSource connection which takes the parameter entered in the textbox to check the value. It doesn’t seem to send to the database and check the values.


The pieces of code :

 SQL Stmt in SqlDataSource1

SELECT InvoiceNo FROM [Order] WHERE (InvoiceNo = @invoiceno)

code in the invoice no method

string searchby = ddlSearchBy.SelectedValue.ToString();

string invoiceno = txtDetail.Text;

 

if (searchby == ("InvoiceNo"))

{

txtDetail.Text = ("@invoiceno");

 

SqlDataSource tester =SqlDataSource1;

SqlDataReader rdr = null ;

rdr = SqlDataSource1.Select();

 If anyone can help id really appreciate it

 

Thanks

Pete