R – ASP.NET Custom Controls

asp.netcustom-server-controls

How do you create a custom control (not an ASCX control) and, more importantly, use it in your project? I'd prefer not to create a separate project for it or compile it as a DLL

Best Answer

Server controls should be compiled into a DLL. There should be no reason to be afraid of having an additional assembly in your project, and it helps create good project organization.

ASP.NET Server controls are actually custom classes in an assembly. They do not have an "ascx" markup file associated to them.

To use a ASP.NET Server Control, you need to tell ASP.NET where to look for its class.

First, create a Class Library project and add it to your solution, I'll call mine "CustomControls.dll".

Once there, add a simple class to be your webcontrol:

public class Hello : System.Web.UI.WebControl
{
    public override Render(HtmlTextWriter writer)
    {
        writer.Write("Hello World");
        base.Render(writer);
    }
}

Build your project, and add it as a reference to your main web project.

Now, in the ASPX page that you want to use this control, you need to register it, so add this as the first line in the aspx AFTER the Page Directive:

<%@ Register TagPrefix="Example" Namespace="CustomControls" Assembly = "CustomControls" %>

Now, you should have a control named <Example:Hello> available to you. It might take it a minute to show up in intellisense.

Related Solutions

Asp.net-mvc – A potentially dangerous Request.Form value was detected from the client

I think you are attacking it from the wrong angle by trying to encode all posted data.

Note that a "<" could also come from other outside sources, like a database field, a configuration, a file, a feed and so on.

Furthermore, "<" is not inherently dangerous. It's only dangerous in a specific context: when writing strings that haven't been encoded to HTML output (because of XSS).

In other contexts different sub-strings are dangerous, for example, if you write an user-provided URL into a link, the sub-string "javascript:" may be dangerous. The single quote character on the other hand is dangerous when interpolating strings in SQL queries, but perfectly safe if it is a part of a name submitted from a form or read from a database field.

The bottom line is: you can't filter random input for dangerous characters, because any character may be dangerous under the right circumstances. You should encode at the point where some specific characters may become dangerous because they cross into a different sub-language where they have special meaning. When you write a string to HTML, you should encode characters that have special meaning in HTML, using Server.HtmlEncode. If you pass a string to a dynamic SQL statement, you should encode different characters (or better, let the framework do it for you by using prepared statements or the like)..

When you are sure you HTML-encode everywhere you pass strings to HTML, then set ValidateRequest="false" in the <%@ Page ... %> directive in your .aspx file(s).

In .NET 4 you may need to do a little more. Sometimes it's necessary to also add <httpRuntime requestValidationMode="2.0" /> to web.config (reference).

C# – How to create a dropdownlist from an enum in ASP.NET MVC

For MVC v5.1 use Html.EnumDropDownListFor

@Html.EnumDropDownListFor(
    x => x.YourEnumField,
    "Select My Type", 
    new { @class = "form-control" })

For MVC v5 use EnumHelper

@Html.DropDownList("MyType", 
   EnumHelper.GetSelectList(typeof(MyType)) , 
   "Select My Type", 
   new { @class = "form-control" })

For MVC 5 and lower

I rolled Rune's answer into an extension method:

namespace MyApp.Common
{
    public static class MyExtensions{
        public static SelectList ToSelectList<TEnum>(this TEnum enumObj)
            where TEnum : struct, IComparable, IFormattable, IConvertible
        {
            var values = from TEnum e in Enum.GetValues(typeof(TEnum))
                select new { Id = e, Name = e.ToString() };
            return new SelectList(values, "Id", "Name", enumObj);
        }
    }
}

This allows you to write:

ViewData["taskStatus"] = task.Status.ToSelectList();

by using MyApp.Common