Evaluating/Validating Paramaters In A SqlDataSource

I want to do some error checking on the parameters found in a SQLDataSource before I run the insert.  The problem is these are ControlParameters and I want to do this dynamically so I can't just call the Control.Text property and grab its value. So how can I get access to what the ControlParameter evaluates to?

Secondly, is there a way to access what the update parameters evaluate to in order to check them before they're inserted - if so how do I get access to these?

Here's an example of one of the data sources i'm using:<asp:SqlDataSource ID="sqlContact" runat="server" ConnectionString="<%$ ConnectionStrings:strConn %>"

SelectCommand="SELECT [ContactID], [FirstName], [LastName], , [Address], [Phone], [Grade], [Contacted], [ListServe] FROM [Contact]"

UpdateCommand="UPDATE Contact SET FirstName = @FirstName, LastName = @LastName, Email = @Email, Address = @Address, Phone = @Phone, Grade = @Grade WHERE ContactID = @ContactID"

DeleteCommand="DELETE FROM [Contact] WHERE ContactID = @ContactID"

InsertCommand="INSERT INTO [Contact] ([FirstName],[LastName],,[Address],[Phone],[Grade],[Contacted],[ListServe]) VALUES (@FirstName,@LastName,@Email,@Address,@Phone,@Grade,0,0)">

<UpdateParameters>

<asp:Parameter Name="FirstName" Type="String" />

<asp:Parameter Name="LastName" Type="String" />

<asp:Parameter Name="Email" Type="String" />

<asp:Parameter Name="Address" Type="String" />

<asp:Parameter Name="Phone" Type="String" />

<asp:Parameter Name="Grade" Type="String" />

</UpdateParameters>

<InsertParameters>

<asp:ControlParameter Name="FirstName" Type="String" ControlID="txtContactFirst" PropertyName="Text" />

<asp:ControlParameter Name="LastName" Type="String" ControlID="txtContactLast" PropertyName="Text" />

<asp:ControlParameter Name="Email" Type="String" ControlID="txtContactEmail" PropertyName="Text" />

<asp:ControlParameter Name="Address" Type="String" ControlID="txtContactAddress" PropertyName="Text" />

<asp:ControlParameter Name="Phone" Type="String" ControlID="txtContactPhone" PropertyName="Text" />

<asp:ControlParameter Name="Grade" Type="String" ControlID="ddlContactGrade" PropertyName="SelectedValue" />

</InsertParameters>

</asp:SqlDataSource>

 An Event is fired when I click add on a button which looks similar to this:

//Add btnAddContact_Clickprotected void btnAddContact_Click(object sender, EventArgs e)

{

InsertRow(sqlContact);

}The InsertRow() function is then what i'm using to evaluate the values...  So how can get the values those controlparameters actually are in order to evaluate them before I actually insert.  Or is there a better way to do it?