PageindexChanging TargetInvocationExeption

I'm having a little bit of trouble sorting out the paging scenario with a gridview i.e. I can't get the bloody thing to show page, 2, 3, 4, etc.

I have the following Grid view code

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" 
               style="z-index: 1; left: 20px; top: 440px; position: absolute; height: 133px; " 
        AllowPaging="True" AllowSorting="True" Font-Size="Small" 

        PageSize="2" onpageindexchanging="Gr开发者_如何转开发idView1_PageIndexChanging">
        <Columns>

With the following

  protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
{
    GridView1.PageIndex = e.NewPageIndex;
    GridView1.DataBind();
}

Now, I am getting a "TargetinvocationException was unhandled by user code."

Being a newbie, this is beyond my current capabilities and has confused me somewhat. How do I go about binding my gridview properly to allow for the paging to be operate correctly?

---

this is where things get interesting! I am using a linq data source:

<asp:LinqDataSource ID="**lqPackWeights**" runat="server"
        ContextTypeName="ORWeightsDataClassesDataContext" 
        Select="new (UnitId, UnitDescription, PackagingTypeCode, UnitWeight, WeightUnitCode, RecycledContent, IsBiodegradable, Recyclability, RevisionSourceCode, RevisionDate, ExtendedMaterialName, MaterialText, WeightStatus, ProductPercentage, UnitUserfield1, UnitUserfield2, IDDesc, MaterialLevel)" 
        TableName="tblOnlineReportingCOMPLETEWeights" Where="IDDesc == @IDDesc">
    </asp:LinqDataSource>

lqPackWeights being generated through this:

private object GetMaterialData(string MemberKey, string MaterialType, string MaterialLevel, int Count)
{
    ORWeightsDataClassesDataContext db = new ORWeightsDataClassesDataContext();
    var query = db.tblOnlineReportingCOMPLETEWeights
                .Where(x => x.MaterialLevel == MaterialLevel && x.MaterialText == MaterialType && x.MemberId == MemberKey)
                .OrderByDescending(x => x.ProductPercentage).Take(Count);
    return query;
}

protected void btSearch_Click(object sender, EventArgs e) {

    lqPackWeights.WhereParameters.Clear();
    ControlParameter cp = new ControlParameter();
    cp.Type = TypeCode.String;


    if (radBuyer.Checked)
    {
        cp.ControlID = "ddlProd";
        cp.PropertyName = "SelectedValue";
        cp.Name = "IDDesc";
        lqPackWeights.WhereParameters.Add(cp);
        GridView1.DataSourceID = "lqPackWeights";
        GridView1.DataBind();
    }

    else if (radProd.Checked)
    {
        cp.ControlID = "tbxProdAC";
        cp.PropertyName = "Text";
        cp.Name = "IDDesc";
        lqPackWeights.WhereParameters.Add(cp);
        GridView1.DataSourceID = "lqPackWeights";
        GridView1.DataBind();
    }

I suspect I have one too many binds kicking about...as you can probalby tell from my code, this is new territory for me so be gentle with the abuse!

---

Ok, I've read a few places that I need to thrown in the data source so I have now got the following code

 protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
{
    GridView1.PageIndex = e.NewPageIndex;
    GridView1.DataSourceID = "lqPackWeights";
}

Now when I build the page, it works fine, but when I hit page 2 of x, I receive this nasty little message:

Server Error in '/onlineReportingFUNCTIONING' Application.

This provider supports Skip() only over ordered queries returning entities or projections that contain all identity columns, where the query is a single-table (non-join) query, or is a Distinct, Except, Intersect, or Union (not Concat) operation.

What's that about then?!

---

The binding was actually fine. This was finally sorted by adding in a primary key (which I really should have implmented in the first place!)

So if anyone is reading this, cannot get their gridview to page through an objectdatasource, make sure you have a primary key!!!