In the WebGrid provided sample, CustomEditor_WebTextEditor.aspx, it is shown how to bind an image filename to image column WebGrid. Here is the image column definition snippet from the sample:

<ISWebGrid:WebGridColumn Caption="Image" DataMember="ProductImage" Name="ProductImage"
    Width="100px" ColumnType="Image" ImageFormatString="images/products/{0}" 
    EditType="NoEdit">
</ISWebGrid:WebGridColumn>

Using template cell, you could use Bind keyword in the designer to bind the field, as shown in the article "Walkthrough: Configuring a WebGridColumn to use Templated Cell" in the WebGrid documentation.

I use "Template Column ",bind the data of database!
but I can not update this  "Template Column ",can you tell me how to update  "Template Column "
???

  <ISWebGrid:WebGridColumn ColumnType=Template Caption="LGname" Name="LGname"  EditType="TextBox" NewRowEditType="TextBox">
                 <CellTemplate>
                     <asp:TextBox ID="TextBox1" runat="server" Text='<%# Bind("LGname") %>'>'></asp:TextBox>
                  </CellTemplate>                   
                </ISWebGrid:WebGridColumn>

I enclose one simple sample that shows how to update value of a column that set as “TemplateColumn” as attachment. please have the attached sample tested on your end and let us know if you have different scenario.