title: PropertyName must be set to a valid property name of the control named 'ListOfPosts' in ControlParameter 'SubcategoryId'
body: <p>Hi I am trying to create a SQLDataSource with a parameter that has the value of a query string but I keep getting an error that says :</p>
  
  <p>PropertyName must be set to a valid property name of the control named 'ListOfPosts' in ControlParameter 'SubcategoryId'</p>
  
  <p>I can not seem to understand what the propertyName should be.Here is my code:</p>
  
  <pre><code>&lt;asp:SqlDataSource ID="ListOfPosts" runat="server" 
      ConnectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\ASPNETDB.MDF;Integrated Security=True;User Instance=True" 
      ProviderName="System.Data.SqlClient" 
      SelectCommand="SELECT [forum_posts].[PostTitle], [forum_posts].[PostContent], [forum_posts].[PostDate],
      aspnet_Users.Username , forum_subcategories.SubCategoryName
      FROM [forum_posts]
      JOIN aspnet_Users ON [forum_posts].UserId = aspnet_Users.UserId
      JOIN forum_subcategories on forum_posts.SubcategoryId = forum_subcategories.SubCategoryID
      WHERE [forum_posts].SubcategoryId = @SubcategoryId"&gt;
      &lt;SelectParameters&gt;
          &lt;asp:ControlParameter Name="SubcategoryId" ControlID="ListOfPosts" Type="String" DefaultValue='&lt;%= Request.QueryString["post"] %&gt;'/&gt;
      &lt;/SelectParameters&gt;
  &lt;/asp:SqlDataSource&gt;
  </code></pre>