WPF Custom Attached Property

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Introduction

Most of the applications will have different types of users. Based on user type, they can perform operations like Create, Read, Edit, Delete, etc. so when we develop an application, we have to write multiple lines of code to enable and disable the controls for each screen based on logged in user. It is a very time consuming activity in the development phase.

Using attached property, we can simplify this activity in a generic way. This approach will be fit to WPF and Silverlight applications and we have no need to write the logic for every screen.

Sample Requirement

Application will have the below user types:

• Super Admin
• Admin
• Master
• Standard

Screen wise access

Implementation

When we design a screen, we can set the user type to the appropriate control that can perform the action.

Screen Shots

When the logged in user type is “Standard”

When the logged in user type is “Master”

When the logged in user type is “Admin”

When the logged in user type is “Admin”

When the logged in user type is “Super Admin”

Source Code

Main Window

public partial class MainWindow : Window
{
    public MainWindow()
    {
        // Need to set the user type from login screen
        AppCommon.LogedUserType = UserType.SuperAdmin;
        InitializeComponent();           
        userType.Text = "User Type : " + AppCommon.LogedUserType.ToString();
    }
}

User Types

[Flags]
public enum UserType
{
    All=0,
    SuperAdmin=1,
    Admin=2,
    Master=4,
    Standard=8
}

Attached Property

/// Attached property to control the button 
/// enable or diable based on logged in user type
public class UserAcccess : FrameworkElement
{
    public static UserType GetUserAccessType(DependencyObject obj)
    {
        return (UserType)obj.GetValue(UserAccessProperty);
    }
    
    public static void SetUserAccessType(DependencyObject obj, UserType value)
    {
        obj.SetValue(UserAccessProperty, value);
    }
    
    public static readonly DependencyProperty UserAccessProperty =
        DependencyProperty.RegisterAttached("UserAccessType", 
        typeof(UserType), typeof(UserAcccess), new PropertyMetadata
        (UserType.All, new PropertyChangedCallback(UserAcccessnChanged)));
        
    private static void UserAcccessnChanged
    (DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        FrameworkElement userAccess = (FrameworkElement)d;
        if (((UserType)e.NewValue & AppCommon.LogedUserType) == AppCommon.LogedUserType)
            userAccess.IsEnabled = true;
        else
            userAccess.IsEnabled = false;
    }
}