Getting error while updating LINQDatasource - linq

Question

When I try to update a LINQ data source bound to a grid view, I get the following error:
Could not find a row that matches the given keys in the original values stored in ViewState. Ensure that the 'keys' dictionary contains unique key values that correspond to a row returned from the previous Select operation.
I have specified DataKeyNames in the grid view.
Here's the HTML:
<asp:GridView ID="TaskGridView" runat="server" AutoGenerateColumns="False"
DataKeyNames="taskid,statusid,taskdescription" DataSourceID="GridDataSource"
onrowcreated="TaskGridView_RowCreated">
<Columns>
<asp:TemplateField HeaderText="taskid" InsertVisible="False"
SortExpression="taskid">
<ItemTemplate>
<asp:Label ID="TaskId" runat="server" Text='<%# Bind("taskid") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="taskdescription"
SortExpression="taskdescription">
<EditItemTemplate>
<asp:TextBox ID="TextBox1" runat="server" Text='<%# Bind("taskdescription") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="TaskDesc" runat="server" Text='<%# Bind("taskdescription") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="url" HeaderText="url" SortExpression="url" />
<asp:TemplateField HeaderText="Status">
<ItemTemplate>
<asp:DropDownList runat="server" ID="ddStatus" DataSourceID="DropDownDataSource" DataValueField="statusid" SelectedValue="<%# Bind('Statusid') %>" DataTextField="statusdescription" ></asp:DropDownList>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
<asp:LinqDataSource ID="GridDataSource" runat="server"
ContextTypeName="DailyTask.DailyTaskDBDataContext" TableName="tbl_tasks"
EnableUpdate="True">
</asp:LinqDataSource>
<asp:Button ID="btnUpdate" runat="server" onclick="btnUpdate_Click"
Text="Update" />
<asp:LinqDataSource ID="DropDownDataSource" runat="server"
ContextTypeName="DailyTask.DailyTaskDBDataContext" TableName="tbl_status">
</asp:LinqDataSource>
Here's the corresponding code:
protected void btnUpdate_Click(object sender, EventArgs e)
{
ListDictionary keyValues = new ListDictionary();
ListDictionary newValues = new ListDictionary();
ListDictionary oldValues = new ListDictionary();
try
{
keyValues.Add("taskid", ((Label)TaskGridView.Rows[0].FindControl("TaskId")).Text);
oldValues.Add("taskdescription", ((Label)TaskGridView.Rows[0].FindControl("TaskDesc")).Text);
newValues.Add("taskdescription", "New Taskk");
GridDataSource.Update(keyValues, newValues, oldValues);
}
catch (Exception ex)
{
Response.Write(ex.Message);
}
}

Answer 1

I got the problem it was in the code
I just have to use int.Parse() here because taskid is primary key
keyValues.Add("taskid", int.Parse(((Label)TaskGridView.Rows[0].FindControl("TaskId")).Text));