I have sp grid view in my application page, I am binding some data to the sp grid vie, now I want to apply filtering for this grid.I tried the following code, I am getting error when I click the filtering button in the grid view as shown in the below image. Please Help me. I am struck with this problem since 2 days

![Error](https://i.stack.imgur.com/PaTq1.png)

I used the following code for Filtering

```
 string FilterExpression
        {
            get
            {
                if (ViewState["FilterExpression"] == null)
                {
                    ViewState["FilterExpression"] = "";
                }

                return (string)ViewState["FilterExpression"];
            }
            set
            {
                string thisFilterExpression = "(" + value.ToString() + ")";
                List<string> fullFilterExpression = new List<string>();

                if (ViewState["FilterExpression"] != null)
                {
                    string[] fullFilterExp = ViewState["FilterExpression"].ToString().Split(_ssep, StringSplitOptions.RemoveEmptyEntries);
                    fullFilterExpression.AddRange(fullFilterExp);

                    //if the filter is gone expression already exist?
                    int index = fullFilterExpression.FindIndex(s => s.Contains(thisFilterExpression));
                    if (index == -1)
                    { fullFilterExpression.Add(thisFilterExpression); }
                }
                else
                {
                    fullFilterExpression.Add(thisFilterExpression);
                }
                //loop through the list<T> and serialize to string
                string filterExp = string.Empty;
                fullFilterExpression.ForEach(s => filterExp += s + " AND ");
                filterExp = filterExp.Remove(filterExp.LastIndexOf(" AND "));
                if (!filterExp.EndsWith("))") && filterExp.Contains("AND"))
                {
                    filterExp = "(" + filterExp + ")";
                }
                ViewState["FilterExpression"] = filterExp;
            }
        }

 public DataTable GetDataForFiltering()
        {
            string siteUrl = SPContext.Current.Web.Url;
            using (SPSite oSite = new SPSite(siteUrl))
            {
                using (SPWeb oWeb = oSite.OpenWeb())
                {
                    SPList oListSCat = oWeb.Lists["listHelpDesk"];
                    SPListItemCollection olistItemColl = oListSCat.Items;
                    if (!dt.Columns.Contains("Functional Area"))
                    {
                        dt.Columns.Add("FunctionalArea");
                    }
                    if (!dt.Columns.Contains("Category"))
                    {
                        dt.Columns.Add("Category");
                    }
                    if (!dt.Columns.Contains("SubCategory"))
                    {
                        dt.Columns.Add("SubCategory");
                    }
                    if (!dt.Columns.Contains("Tier"))
                    {
                        dt.Columns.Add("Tier");
                    }
                    //if (!dt.Columns.Contains("Region"))
                    //{
                    //    dt.Columns.Add("Region");
                    //}
                    if (!dt.Columns.Contains("Status"))
                    {
                        dt.Columns.Add("Status");
                    }
                    if (!dt.Columns.Contains("Subject"))
                    {
                        dt.Columns.Add("Subject");
                    }
                    if (!dt.Columns.Contains("Description"))
                    {
                        dt.Columns.Add("Description");
                    }
                    if (!dt.Columns.Contains("Attachments"))
                    {
                        dt.Columns.Add("Attachments");
                    }
                    foreach (SPListItem listItem in olistItemColl)
                    {
                        DataRow dr = dt.NewRow();

                        string fncArea = listItem["Functional Area"].ToString();
                        dr["FunctionalArea"] = fncArea.Split('#')[1];
                        string cat = listItem["Category"].ToString();
                        dr["Category"] = cat.Split('#')[1];
                        string scat = listItem["Subcategory"].ToString();
                        dr["SubCategory"] = scat.Split('#')[1];
                        string tier = listItem["Tier"].ToString();
                        dr["Tier"] = tier.Split('#')[1];
                        //string region = listItem["Region"].ToString();
                        //dr["Region"] = region.Split('#')[1];

                        dr["Status"] = listItem["Status"].ToString();
                        dr["Subject"] = listItem["Subject"].ToString();
                        dr["Description"] = listItem["Description"].ToString();
                        dr["Attachments"] = "Download link";
                        dt.Rows.Add(dr);

                    }
                    return dt;

                }
            }
        }

        public void Filtering()
        {
            try
            {
                objDS = new ObjectDataSource();
                objDS.ID = "objDSWaitingApprovals";
                objDS.SelectMethod = "GetDataForFiltering";
                objDS.TypeName = this.GetType().AssemblyQualifiedName;
                objDS.EnableViewState = false;

                //pass the SortExpression to the select method
                //objDS.SortParameterName = "SortExpression";

                //this resets the dropdown options for other columns after a filter is selected
                objDS.FilterExpression = FilterExpression;
                //add the data source
                Controls.Add(objDS);
                spgrdView.EnableViewState = false;
                //filtering 
                spgrdView.AllowFiltering = true;
                spgrdView.FilterDataFields = "FunctionalArea,Category,SubCategory,Tier,Subject,Description,Attachments,Status";
                spgrdView.FilteredDataSourcePropertyName = "FilterExpression";
                spgrdView.FilteredDataSourcePropertyFormat = "{1} = '{0}'";
                spgrdView.DataSourceID = objDS.ID;
                spgrdView.DataBind();
            }

            catch (Exception ex)
            {
                Page.ClientScript.RegisterClientScriptBlock(typeof(SPAlert), "alert", "<script language=\"javascript\">alert('" + ex.Message + " .')</script>");
            }
        }

 public void spgrdView_OnRowDataBound(object sender, GridViewRowEventArgs e)
        {
            //if (sender == null || e.Row.RowType != DataControlRowType.Header)
            //{
            //    return;
            //}

            SPGridView grid = sender as SPGridView;

            if (String.IsNullOrEmpty(grid.FilterFieldName))
            {
                return;
            }

            // Show icon on filtered column
            for (int i = 0; i < grid.Columns.Count; i++)
            {
                DataControlField field = grid.Columns[i];

                if (field.SortExpression == grid.FilterFieldName)
                {
                    Image filterIcon = new Image();
                    filterIcon.ImageUrl = "/_layouts/images/filter.gif";
                    filterIcon.Style[HtmlTextWriterStyle.MarginLeft] = "2px";

                    // If we simply add the image to the header cell it will
                    // be placed in front of the title, which is not how it
                    // looks in standard SharePoint. We fix this by the code 
                    // below.
                    Literal headerText = new Literal();
                    headerText.Text = field.HeaderText;

                    PlaceHolder panel = new PlaceHolder();
                    panel.Controls.Add(headerText);
                    panel.Controls.Add(filterIcon);

                    e.Row.Cells[i].Controls[0].Controls.Add(panel);

                    break;
                }
            }
}

```