How to handle empty CONTAINS() query parameter in ASP.NET SqlDataSource?

Question

How can we handle empty ControlParameter values in SQL CONTAINS() condition without using code-behind (so that it returns all results)? Looking probably for something like LIKE '%' or WHERE (1=1) .

<asp:TextBox ID="tbSearch" runat="server" placeholder="Search" ></asp:TextBox>

<asp:SqlDataSource ID="SqlDataSourceA" runat="server" ConnectionString="..." 
  SelectCommand="SELECT [Columns] FROM [Table] 
                 WHERE CONTAINS([Column],@searchText) ORDER BY [Time] DESC">
   <SelectParameters>
      <asp:ControlParameter Name="searchText" ControlID="tbSearch" 
                            PropertyName="Text" DefaultValue="?" />
   </SelectParameters>        
</asp:SqlDataSource>

I know that one way is to create a dynamic query in code behind, but maybe there's other way to do that with just markup.

EDIT: ControlParameter default value is empty string.

Answer 1

看看mssql的IS NULL属性

Answer 2

Make the WHERE something like WHERE CONTAINS([Column], COALESCE(@searchText, [Column])) Basically the idea is that if @searchText is null, use [Column] , and [Column] contains [Column] so everything should be returned.

Might have issues if @searchText isn't null but just blank, you'd have use a CASE statement to check for length or something similar.

For empty string handling, I couldn't get the 2nd param of CONTAINS to accept a case statement, so this should work: WHERE [COLUMN] = CASE WHEN LEN(RTRIM(LTRIM(COALESCE(@searchText, '')))) = 0 THEN [COLUMN] ELSE @searchText END Obviously you can then change the '=' to LIKE if needed.