How to solve invalidoperationexception was caught error

protected void btnUpdate_Click(object sender, EventArgs e)
    {

        try
        { 
        string cs = ConfigurationManager.ConnectionStrings["SSMS"].ConnectionString;
        SqlConnection con = new SqlConnection(cs);

        SqlDataAdapter da = new SqlDataAdapter((string)ViewState["SELECT_QUERY"],con);
      SqlCommandBuilder builder = new SqlCommandBuilder(da);

        DataSet ds=(DataSet)ViewState["DATASET"];
        if (ds.Tables["Students"].Rows.Count > 0)
        {
            DataRow dr = ds.Tables["Students"].Rows[0];
            dr["Name"] = txtStudentName.Text;
            dr["Gender"] = ddlGender.SelectedItem;
            dr["TotalMarks"] = txtTotalMarks.Text;
            dr["Id"] = txtStudentId.Text;
        }
        
        da.Update(ds, "Students");
        }
        catch(Exception Ex)
        {

        }
    }
}