In this article I will explain with an example, how to use NULL Parameters with SqlDataSource and how to pass NULL parameters to StoredProcedure using SqlDataSource in ASP.Net.
In this article, a GridView will be populated and filtered using a StoredProcedure and SqlDataSource in ASP.Net.
Here I am making use of Microsoft’s Northwind Database. The download and install instructions are provided in the following article.
The following StoredProcedure accepts a NULL parameter @CustomerID and its value is used to fetch the Customer from the Customers table of the Northwind database.
It is termed as NULL parameter, since if the value of the parameter is passed blank or empty string then the parameter value will be passed as NULL and it will return all records present in the table.
CREATEPROCEDURE [dbo].[Customers_GetCustomer]
      @CustomerID NVARCHAR(30)
      SELECT CustomerId
      FROM Customers
      WHERE (CustomerID = @CustomerID OR @CustomerID ISNULL)
Passing NULL parameter to StoredProcedure using SqlDataSource in ASP.Net
The following HTML Markup consists of an ASP.Net GridView control, a TextBox and a Button.
The GridView is populated with records from the Customers table of the Northwind database using SqlDataSource.
The SqlDataSource has been set with following properties.
SelectCommand – Name of the StoredProcedure to be executed.
SelectCommandType – Value set as StoredProcedure. Default value is Text.
CancelSelectOnNullParameter – If not set to False, then the SELECT query will be cancelled for NULL parameter values. Default value is True.
The SqlDataSource also has a SelectParameter. Here SelectParameter of type ControlParameter is used as the value of an ASP.Net control i.e. TextBox needs to be passed as parameter.
The ControlParameter is set with the following properties.
Name – Name of the parameter being passed to StoredProcedure. The name of the parameter must be exact same as the StoredProcedure parameter name.
ControlID – ID of the control whose value will be passed as Parameter.
DefaultValue – The StoredProcedure used in this article displays all records when the parameter value is blank or empty string and the default value is set to blank.
ConvertEmptyStringToNull – As the name suggests it will pass blank or empty string as NULL if set to True. Since here blank or empty string needs to be passed, the value is set to False.
Customer ID:
<asp:TextBox ID="txtSearch" runat="server"></asp:TextBox>
<asp:Button ID="btnSearch" runat="server" Text="Search" />
<hr />
<asp:GridView ID="GridView1" HeaderStyle-BackColor="#3AC0F2" HeaderStyle-ForeColor="White"
    runat="server" AutoGenerateColumns="false" DataSourceID="GridDataSource" AllowPaging="true">
        <asp:BoundField DataField="ContactName" HeaderText="Name" ItemStyle-Width="150" />
        <asp:BoundField DataField="City" HeaderText="City" ItemStyle-Width="150" />
        <asp:BoundField DataField="Country" HeaderText="Country" ItemStyle-Width="150" />
<asp:SqlDataSource ID="GridDataSource" runat="server" ConnectionString="<%$ ConnectionStrings:ConStr %>"
    SelectCommand="Customers_GetCustomer" SelectCommandType="StoredProcedure" CancelSelectOnNullParameter="false">
        <asp:ControlParameter Name="CustomerID" ControlID="txtSearch" PropertyName="Text" DefaultValue="" ConvertEmptyStringToNull="false" />
GridView displaying all records
SqlDataSource NULL Parameters: Pass NULL parameters to Stored Procedure using SqlDataSource in ASP.Net
GridView records filtered using StoredProcedure using NULL Parameter
SqlDataSource NULL Parameters: Pass NULL parameters to Stored Procedure using SqlDataSource in ASP.Net