Convert to Thumbnail by dynamically resizing Picture Image and display it in ASP.Net GridView

hi 

i use these code for resizing image

behind code

    public string img_resize(string picname, int maxHeight, int maxWidth)
    {

        System.Drawing.Image currentImage = System.Drawing.Image.FromFile(server.mappath("mypics\\") + picname);

        double imgHeight = 0;
        double imgWidth = 0;
        imgHeight = currentImage.Height;
        imgWidth = currentImage.Width;

        if (imgWidth > maxWidth | imgHeight > maxHeight)
        {
            //Determine what dimension is off by more
            double deltaWidth = imgWidth - maxWidth;
            double deltaHeight = imgHeight - maxHeight;
            double scaleFactor = 0;

            if (deltaHeight > deltaWidth)
            {
                //Scale by the height
                scaleFactor = maxHeight / imgHeight;
            }
            else
            {
                //Scale by the Width
                scaleFactor = maxWidth / imgWidth;
            }

            imgWidth *= scaleFactor;
            imgHeight *= scaleFactor;
        }

        string html = null;

        html = "<img src=\"" + picname + "\" height=\"" + imgHeight + "\" width=\"" + imgWidth + ">\"";

        return html;


    }


    public void img_resize(string picname, int maxHeight, int maxWidth)
    {

        System.Drawing.Image currentImage = System.Drawing.Image.FromFile(Server.MapPath("image/house\\") + picname);
       double imgHeight = 0;
         double imgWidth = 0;
        imgHeight = currentImage.Height;
        imgWidth = currentImage.Width;

        if (imgWidth > maxWidth | imgHeight > maxHeight)
        {
            //Determine what dimension is off by more
            double deltaWidth = imgWidth - maxWidth;
            double deltaHeight = imgHeight - maxHeight;
            double scaleFactor = 0;

            if (deltaHeight > deltaWidth)
            {
                //Scale by the height
                scaleFactor = maxHeight / imgHeight;
            }
            else
            {
                //Scale by the Width
                scaleFactor = maxWidth / imgWidth;
            }

            imgWidth *= scaleFactor;
            imgHeight *= scaleFactor;
        }



        string html = null;
        html = "<img src=\""  + picname + "\" height=\"" + imgHeight + "\" width=\"" + imgWidth + ">\"";

       


    }

design view

    <asp:GridView ID="GridView3" runat="server" AllowPaging="True" AllowSorting="True"AutoGenerateColumns="False" DataKeyNames="reply_pk" DataSourceID="reply_source"Width="100%" GridLines="None">
            <Columns>
<asp:TemplateFieldSortExpression="reply_user">
                          
                 <ItemTemplate>
                                 <%#img_resize(Eval("my_img"),100, 80)%>
                                                   
                </ItemTemplate>
        </asp:TemplateField>
    </Columns>
 </asp:GridView>

but in this line occur error 

       <ItemTemplate> <%#img_resize(Eval("my_img"),100, 80)%> </ItemTemplate>

error:

Parser Error

Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately. 

Parser Error Message: The server tag is not well formed.

what should i do ?

best regards