Sorting with Up and Down icons

1. First we need to create two variables in ViewState to store current direction and expression:

<br />
public string CurrentSortExpression<br />
        {<br />
            get<br />
            {<br />
                if (ViewState["sortExpression"] != null)<br />
                {<br />
                    return ViewState["sortExpression"].ToString();<br />
                }<br />
                else<br />
                {<br />
                    ViewState["sortExpression"] = string.Empty;<br />
                    return string.Empty;<br />
                }<br />
            }<br />
            set<br />
            {<br />
                ViewState["sortExpression"] = value;<br />
            }<br />
        }<br />
<br />
        public string CurrentSortDirection<br />
        {<br />
            get<br />
            {<br />
                if (ViewState["sortDirection"] != null)<br />
                {<br />
                    return ViewState["sortDirection"].ToString();<br />
                }<br />
                return string.Empty;<br />
            }<br />
            set<br />
            {<br />
                ViewState["sortDirection"] = value;<br />
            }<br />
        }<br />

2. Then we have to implement handler to attach sort icons to header rows:

<br />
protected void GridViewSortImages(object sender, GridViewRowEventArgs e)<br />
        {<br />
            GridView senderGridView = (GridView)sender;<br />
            Literal space = new Literal();<br />
            space.Text = "    ";<br />
            if (e.Row != null && e.Row.RowType == DataControlRowType.Header)<br />
            {<br />
                for(int i=0;i<gvusers.columns.count;i++)><br />
                {<br />
                    TableCell cell = e.Row.Cells[i];<br />
                    DataControlField column=gvUsers.Columns[i];<br />
  <br />
                    if (cell.HasControls())<br />
                    {<br />
                        LinkButton button = cell.Controls[0] as LinkButton;<br />
                        if (button != null)<br />
                        {<br />
                            Image image = new Image();<br />
                            image.ImageUrl = "~/AdminUI/Images/icon-sort_default.gif";<br />
                            if (CurrentSortExpression==column.SortExpression)<br />
                            {<br />
                                if (CurrentSortDirection=="asc")<br />
                                    image.ImageUrl = "~/AdminUI/Images/icon-sort1.gif";<br />
                                else if (CurrentSortDirection=="desc")<br />
                                    image.ImageUrl = "~/AdminUI/Images/icon-sort2.gif";<br />
                            }<br />
                            cell.Controls.Add(image);<br />
                        }<br />
                    }<br />
                }<br />
            }<br />
        }<br />

3. Farther let's make some logic in Sorting handler for our GridView:

<br />
protected void gvUsers_Sorting(object sender, GridViewSortEventArgs e)<br />
        {<br />
            if (CurrentSortExpression == e.SortExpression.ToString())<br />
            {<br />
                if (CurrentSortDirection == "asc")<br />
                    CurrentSortDirection = "desc";<br />
                else<br />
                    CurrentSortDirection = "asc";<br />
            }<br />
            else<br />
            {<br />
                CurrentSortExpression = e.SortExpression.ToString();<br />
                CurrentSortDirection = "asc";<br />
            }<br />
<br />
            BindUsers(0, CurrentSortExpression, (CurrentSortDirection == "asc")?true:false);<br />
        }<br />

4. And at last lets use GridViewSortImages in RowCreated event:

<br />
protected void gvUsers_RowCreated(object sender, GridViewRowEventArgs e)<br />
        {<br />
            // Some code<br />
            GridViewSortImages(sender, e);<br />
        }<br />