Question

I am trying to create localization for my ASP.NET code, but I have issues setting the TemplateField’s HeaderText

I have this that works

                        <asp:TemplateField HeaderText="Description">
                        <ItemTemplate>
                            <%# Eval("Description") %>
                        </ItemTemplate>
                        <FooterTemplate>
                            <asp:Panel ID="Panel5" runat="server" DefaultButton="EditSubmission">
                                <asp:TextBox runat="server" ID="Submission_DescriptionTxtBox" TextMode="MultiLine"
                                ToolTip='<%# GetById("atforbedringsforslag_description_tooltip") %>'/>

                                </asp:Panel>
                        </FooterTemplate>
                    </asp:TemplateField>

But I want to change

<asp:TemplateField HeaderText="Description">

To

<asp:TemplateField HeaderText='<%# GetById("atforbedringsforslag_description_title") %>'>

But then I get

Databinding expressions are only supported on objects that have a DataBinding event. System.Web.UI.WebControls.TemplateField does not have a DataBinding event.

How should I set this field? I can find some that uses OnRowCreated, but then you access the fields with an index number, and then it becomes easy to make mistakes or forgot to change indexes if new fields are added later on

---

EDIT My solution:

Created the custom expression builder

using System.Web.Compilation;
using System;
using System.CodeDom;

public class LocalizationExpressionBuilder : ExpressionBuilder
{
    public override CodeExpression GetCodeExpression(System.Web.UI.BoundPropertyEntry entry, object parsedData, ExpressionBuilderContext context)
    {
        CodeExpression[] inputParams = new CodeExpression[] { new CodePrimitiveExpression(entry.Expression.Trim()), 
                                                    new CodeTypeOfExpression(entry.DeclaringType), 
                                                    new CodePrimitiveExpression(entry.PropertyInfo.Name) };

        // Return a CodeMethodInvokeExpression that will invoke the GetRequestedValue method using the specified input parameters 
        return new CodeMethodInvokeExpression(new CodeTypeReferenceExpression(this.GetType()),
                                    "GetRequestedValue",
                                    inputParams);
    }

    public static object GetRequestedValue(string key, Type targetType, string propertyName)
    {
        // If we reach here, no type mismatch - return the value 
        return GetByText(key);
    }

    //Place holder until database is build
    public static string GetByText(string text)
    {
        return text;
    }
}

Added the prefix to my web.config

<system.web>
<compilation debug="true" defaultLanguage="c#" targetFramework="4.0">
  <expressionBuilders>
    <add expressionPrefix="localizeByText" type ="LocalizationExpressionBuilder"/>
  </expressionBuilders>
    </compilation>
</system.web>

And I can now get my text like this

<asp:TemplateField HeaderText='<%$ localizeByText:Some text %>'>

Answer 1

You can build your own custom Expression Builder which calls your GetById method. Look at the following link for an old but good article explaining how to build an expression builder and how to use it:

https://web.archive.org/web/20210304125044/https://www.4guysfromrolla.com/articles/022509-1.aspx

When you have an expression builder, you use it with the <%$ syntax. This is different from the databinding syntax <%#.

For the HeaderText field, it is not allowed to use DataBinding syntax (not sure why, but that’s how MS made it). Using expression syntax IS allowed and will work once you have your custom expression builder done.

Do go through the page I linked to, it’s quite a lot of text, but in the end making you expression builder will not take much effort…

Also, the page has a link at the bottom to a library of expression builder that the author has made. Have a look at them, maybe one of them could be used directly to solve your problem (specifically, the CodeExpressionBuilder).