How to validate a URL in ASP.NET?

By Regular expression data annotation in Model class

[RegularExpression(@"^(http|https|ftp)\://([a-zA-Z0-9\.\-]+(\:[a-zA-Z0-9\.&%\$\-]+)*@)*((25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[1-9])\.(25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[1-9]|0)\.(25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[1-9]|0)\.(25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[0-9])|localhost|([a-zA-Z0-9\-]+\.)*[a-zA-Z0-9\-]+\.(com|edu|gov|int|mil|net|org|biz|arpa|info|name|pro|aero|coop|museum|[a-zA-Z]{2}))(\:[0-9]+)*(/($|[a-zA-Z0-9\.\,\?\'\\\+&%\$#\=~_\-]+))*$", ErrorMessage = "Invalid url")]
public string Url { get; set; }

How to set Max length for an input in ASP.NET MVC

By StringLength data annotation

[StringLength(20, ErrorMessage = "Name cannot be longer than 20 characters.")]
public string Name { get; set; }

How to use TextArea for @Html.EditorFor in ASP.NET MVC?

Two ways:
1. Add data annotation in Model class
[DataType(DataType.MultilineText)]
public string Text { get; set; }

2. @Html.TextAreaFor(model => model.Text)

How to change EditFor width in ASP.NET MVC 3?

Should be very simple? But need to two steps to do so:
1. Replace EditFor with TextBoxFor
2. Pass html property into TextBoxFor

@Html.TextBoxFor(m => m.Name, new {style = "width:50px"})

How to add data annotations to a class without changing it?

By MetadataType class
- Inherent from it, make it to be base class
- Then use metadata class to add validation data annotations in subclass

[MetadataType(typeof(ModelMetadata))]
public class Model : Base_Class {
}


internal class ModelMetadata {
    [Required]
    public string Name { get; set; }
}