Question

I have a dropdownlist with following options:

                                    <asp:DropDownList ID="ddlTaxStatus" runat="server" OnPreRender="ddlContainerStatus_PreRender">
                                    <asp:ListItem Text="--Select--" Value="-1"></asp:ListItem>
                                    <asp:ListItem Value="" Text="'' - Not closed"></asp:ListItem>
                                    <asp:ListItem Value="R" Text="R - Ready to pay"></asp:ListItem>
                                    <asp:ListItem Value="X" Text="X - Paid"></asp:ListItem>
                                    <asp:ListItem Value="C" Text="C - Cancel"></asp:ListItem>
                                    <asp:ListItem Value="O" Text="O - Original"></asp:ListItem>
                                    <asp:ListItem Value="D" Text="D - Delete"></asp:ListItem>
                                </asp:DropDownList>

Based on option selected by user, I send the selected option for search in my database and retrieve records which has the selected value in the related field. My Sql usp looks like this:

 ALTER PROCEDURE [dbo].[uspGetContainerSummaryRecordsForSearch] (
      @fkJobID varchar(8),
      @csmTaxStatus varchar(3)
 )
AS
  BEGIN
      SET TRANSACTION ISOLATION LEVEL SNAPSHOT
      SET NOCOUNT ON;

            SELECT fkJobID,
                      csmContainerID,
                      csmDisplayContainerID,
                      csmTaxStatus

               FROM   ContainerSummaryRecord
               where  fkJobID = @fkJobID
                      AND ( @csmTaxStatus IS NULL
                             OR csmTaxStatus = @csmTaxStatus )

  END 

Now my question, When user selects option with Value=”” and Text=”” – Not closed”, I do not get the desired result. This is because value= “” is actually stored as null in DB.
In query i am comparing input parameter in where clause like this @csmTaxStatus IS NULL
because if user has not selected any option meaning Text=”–Select–” Value=”-1″, then the filter is not applied and all the results get returned (and this is the desired behavior for this option). But this is clashing with the Value=”” which is stored as null in DB. Kindly help.

Answer 1

change where condition as

just make use of isnull() to resolve issue easily which replace null with blank as below

where  fkJobID = @fkJobID                       
AND ( @csmTaxStatus IS NULL                              
     OR isnull(csmTaxStatus,'') = @csmTaxStatus )