How to get a gridview to show all table rows when no text is entered in a dependent textbox?

Question

The below works correctly and filters my gridview based on the text entered in my textbox.

When no text is entered into my textbox I get no results and cannot unders

Answer 1

Instead of coalesce you may have a if block which checks if the @search parameter is empty or not as shown below..

if @search is not empty 
  SELECT  [table].[column]
  FROM    [table]
  WHERE   [table].[column] LIKE '%' + @Search + '%' OR COALESCE(@Search,'') = ''
else
  SELECT  [table].[column]
  FROM    [table]
  WHERE   [table].[column]

Answer 2

Look at CancelSelectOnNullParameter - by default, this prevents the select command from being called when a select parameter's value is null. After setting it to false, the select SP will then still get called even if the text box is empty, e.g.

<asp:SqlDataSource ID="sqlSearch" RunAt="Server" 
    CancelSelectOnNullParameter="false" ...>
</asp:SqlDataSource>

The SqlDataSource seems a bit misleading to me here, because TextBox.Text returns String.Empty when it's empty, not null, therefore I wouldn't expect to have to mess with CancelSelectOnNullParameter for a TextBox, but it seems we have to.