Issue with SQLDataSource and FilterExpression

I'm not sure exactly how the FilterExpression works. I have a sqldatasource, stored procedure, and GridView. My stored procedure basicly a select statement to populate my gridview, it included the fields I want to filter on. In my codebehind file I build a WHERE Clause based on the entries a user makes. Then I add the my FilterExpr variable to the SqlDataSource1.FilterExpression = FilterExpr. My SqlDataSource has a number of control parameters that match the textboxes a users enters into.

My question, I guess is does my stored procedure need the variables matching my controlparameters for my sqldatasource? Or how does this work? My GridView is returning all rows no matter what I enter into the filter textboxes (first, last, etc...)

MY SQLSDATASOURCE

 <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:ConnectionString%>" SelectCommand="ClientSearch" SelectCommandType="StoredProcedure"> <FilterParameters> <asp:ControlParameter ControlID="SearchLastName" Name="LastName" PropertyName="Text" ConvertEmptyStringToNull="true" /> <asp:ControlParameter ControlID="SearchFirstName" Name="FirstName" PropertyName="Text" ConvertEmptyStringToNull="true" /> <asp:ControlParameter ControlID="SearchEmail" Name="Email" PropertyName="Text" ConvertEmptyStringToNull="true" /> <asp:ControlParameter ControlID="SearchAddress" Name="Address" PropertyName="Text" ConvertEmptyStringToNull="true" /> <asp:ControlParameter ControlID="SearchComment" Name="Comment" PropertyName="Text" ConvertEmptyStringToNull="true" /> </FilterParameters> </asp:SqlDataSource>

MY CODEBEHIND

       Dim FilterExprAs String
        If SearchLastName.Text =""And _
            SearchFirstName.Text =""And _
            SearchEmail.Text =""And _
            SearchComment.Text =""And _
            SearchAddress.Text =""Then
            lblMessage.Text ="You didn't enter any search parameters. Please try Again."
            Me.GridViewSearch.DataSourceID = ""
            Exit Sub
        Else
            Me.GridViewSearch.DataSourceID = "SqlDataSource1"
        End If
        FilterExpr = ""
        If SearchLastName.Text <> "" Then
            FilterExpr = FilterExpr & "LastNameLike'" & _
            SearchLastName.Text &"%" &"' AND "
        End If
        If SearchFirstName.Text <> "" Then
            FilterExpr = FilterExpr & "FirstNameLike'" & _
            SearchFirstName.Text &"%" &"' AND "
        End If
        If SearchEmail.Text <> "" Then
            FilterExpr = FilterExpr & "Like'" & _
             SearchEmail.Text &"%" &"' AND "
        End If
        If SearchComment.Text <> "" Then
            FilterExpr = FilterExpr & "[Comments]Like'" & "%" & _
             SearchComment.Text &"%" &"' AND "
        End If
        If SearchAddress.Text <> "" Then
            FilterExpr = FilterExpr & "[Address]Like'" & "%" & _
             SearchAddress.Text &"%" &"' AND "
        End If
        If Right(FilterExpr, 4) = "AND "Then
            FilterExpr = Left(FilterExpr, Len(FilterExpr) - 4)
       End If
        Try
            Me.SqlDataSource1.FilterExpression = FilterExpr
           Me.SqlDataSource1.DataBind()
           Me.GridViewSearch.DataBind()
           Me.lblMessage.Text =Me.SqlDataSource1.FilterExpression
       Catch objExceptionAs SqlException
           Dim objErrorAs SqlError
           For Each objErrorIn objException.Errors
                Response.Write(objError.Message)
           Next
        End Try
    End Sub 

MY SPROC

GOALTER PROCEDURE [dbo].[ClientSearch]ASSELECT C.ClientID, C.FirstName, C.LastName, A.Address, C.Comments, C.EMailFROM tblClient CINNERJOIN tblClientAddresses AON C.ClientID = A.ClientID

Remove all the <FilterParameters> and it should work fine.