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Databinding enumerators to DataBound controls

, 27 Mar 2013
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Databinding enumerators to DataBound controls.

Introduction

The objective is binding Enums to any ListControl, actually to any DataBoundControl such as DropdownList, Repeaters, etc, avoiding indexes hard coding and bad practices... In this brief code I provide you kind of quick workaround that enhance the portability and maintainability of the source code. 

As you will see below, the idea is to have any enum bound, keeping it simple. 

Enums are basically a set of named constants. They are declared in C# using the enum keyword. Every enum type automatically derives from System.Enum and thus we can use System.Enum methods on our Enums.   

Here, we are defining a Mode enum having two values: Iterative and Secuential

enum Mode {Iterative, Secuential}

Using the code 

First of all, we might define the Mode enum members by using DescriptionAttribute within ComponentModel, and IsDefault custom attribute as it is wanted to be shown in the dropdownlist.

public enum Mode
{
    [Description("Iterative option"), IsDefault(true)]
    Iterative,
    [Description("Secuential option"), IsDefault(false)]
    Sequential
} 

An ASP.NET list control can be bound to any data source that implements the IList, IEnumerable, ICollection, here we are binding it adding all the items in the array by using AddRange method. 

The idea is to create an extension method "ToItems" that allows us turn enum values into ListItem[]

this.drpMode.Items.AddRange(typeof(Mode).ToItems()); 

When it is necessary to  get the selected IList value and match it back with the enum value we can perform it by using another extension method. I think this is valid just in .NET 4.0 but in order to keep the feature in previous versions it's added the extension method within. The entire piece of code can be wrapped it into a control when necessary.

Mode value = EnumExtentions.Parse<Mode>(this.drpMode.SelectedValue);

Background

First of all, I found it neat to create a custom default attribute to be annotated it in order to let the dropdownlist know which is the default selected item. 

[AttributeUsage(AttributeTargets.All)]
public class IsDefaultAttribute : Attribute
{
    public bool IsDefault{ get; set; }

    public IsDefaultAttribute(bool isDefault)
    {
	    IsDefault = isDefault;
	}
} 

Finally, by LINQ we query enum both values and annotations and create a ListItem collection as below.

public static ListItem[] ToItems(this Type enumType) {
     var items = from a in enumType.GetFields()
     where !a.IsSpecialName
     select new ListItem()
     {
        Value = a.GetValue(a).ToString(),
        Text = (a.GetCustomAttributes(typeof(DescriptionAttribute), false)[0] 
	as DescriptionAttribute).Description,
        Selected = (a.GetCustomAttributes(typeof(IsDefaultAttribute), false)[0] 
	as IsDefaultAttribute).IsDefault};
     return items.ToArray<ListItem>();
}

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Alejandro Garcia
Systems Engineer
Argentina Argentina
Alejandro has over 9 years of experience designing and developing software, especially using Microsoft technologies.
 
Although he considers himself a software developer, during his career he was involved in all development process’ stages playing different roles within different projects, leading small groups, mentoring junior coders, as a business analyst, as a sofware architect, and as a .net and java developer.

Comments and Discussions

 
GeneralMy vote of 5 PinmemberAlejandro Garcia27-Mar-13 4:20 

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