Object Reference Not set to an instance of an object error

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ASP.NET

i want To count the Column values and then Display in Footer Template.
For that i wrote like this.
But i got the error "Object Reference not set to an instance of an object"

DataTable table = dsProject_SH.Tables[1];
        decimal count = 0;
        foreach (DataRow dr in table.Rows)
        {

            count += Convert.ToDecimal(dr["Weightage"]);
        }

        Label lblWeightage = (Label)dg_Drawing_Appl.FooterRow.FindControl("lblWeightage");        
        lblWeightage.Visible = true;
        lblWeightage.Text = count.ToString();

I'm checking to "Count" data .It's fine But in highlighted line only i'm getting error can any one help me to do this.


Thanks in advance....