Customizing Commands

This article will demonstrate how to customize RadDataForm's commands in an MVVM-friendly way as well as how to execute them manually.

• The DataFormCommandProvider
• Designing a Custom DataFormCommandProvider
• Setting the Custom DataFormCommandProvider
• Executing Commands Manually

The DataFormCommandProvider

The public DataFormCommandProvider class exposes the "execute" and "can-execute" logic of all commands utilized by RadDataForm. RadDataForm processes these commands according to its current provider.

Execute Logic Methods

The methods listed below identify the logic that is executed when a certain command's invocation takes place.

Example 1: The IExecuteLogicMethods

• C#
• VB.NET

void MoveCurrentToFirst(); 
void MoveCurrentToLast(); 
void MoveCurrentToNext(); 
void MoveCurrentToPrevious(); 
void BeginEdit(); 
void CommitEdit(); 
void Delete(); 
void CancelEdit(); 
void AddNew(); 

Sub MoveCurrentToFirst() 
Sub MoveCurrentToLast() 
Sub MoveCurrentToNext() 
Sub MoveCurrentToPrevious() 
Sub BeginEdit() 
Sub CommitEdit() 
Sub Delete() 
Sub CancelEdit() 
Sub AddNew() 

Can-Execute Logic Methods

With the help of those methods you can identify whether a certain command can be executed or not.

Example 2: The ICanExecuteLogicMethods

• C#
• VB.NET

bool CanMoveCurrentToFirstExecute(); 
bool CanMoveCurrentToLastExecute(); 
bool CanMoveCurrentToNextExecute(); 
bool CanMoveCurrentToPreviousExecute(); 
bool CanBeginEditExecute(); 
bool CanCommitEditExecute(); 
bool CanDeleteExecute(); 
bool CanCancelEditExecute(); 
bool CanAddNewExecute(); 

Function CanMoveCurrentToFirstExecute() As Boolean 
Function CanMoveCurrentToLastExecute() As Boolean 
Function CanMoveCurrentToNextExecute() As Boolean 
Function CanMoveCurrentToPreviousExecute() As Boolean 
Function CanBeginEditExecute() As Boolean 
Function CanCommitEditExecute() As Boolean 
Function CanDeleteExecute() As Boolean 
Function CanCancelEditExecute() As Boolean 
Function CanAddNewExecute() As Boolean 

A runnable demo that utilizes the code from this article can be found on the DataForm's CustomCommandsProvider demo.

Designing a Custom DataFormCommandProvider

The first step is to create your own class that inherits from DataFormCommandProvider:

Example 3: Defining a Custom CommandProvider

• C#
• VB.NET

public class CustomCommandProvider : DataFormCommandProvider 
{ 
    public CustomCommandProvider() : base(null) 
    { 
    } 
    public CustomCommandProvider(RadDataForm dataForm) 
            : base(dataForm) 
    { 
        this.DataForm = dataForm; 
    } 
    //. . . 
} 

Public Class CustomCommandProvider 
    Inherits DataFormCommandProvider 
    Public Sub New() 
        MyBase.New(Nothing) 
    End Sub 
    Public Sub New(dataForm As RadDataForm) 
        MyBase.New(dataForm) 
        Me.DataForm = dataForm 
    End Sub 
    '. . . 
End Class 

You need to override the methods of the commands that will be customized. In the following example we will customize: MoveCurrentToNext, MoveCurrentToPrevious, BeginEdit and CancelEdit.

MoveCurrentToNext and MoveCurrentToPrevious

We aim at changing their execution logic, in order to start editing the item, as soon as it was set as a current one and bypass the logic in the same place. Here are the overridden methods:

Example 4: Customizing MoveCurrentToNext and MoveCurrentToPrevious

• C#
• VB.NET

protected override void MoveCurrentToNext() 
{ 
    if (this.DataForm != null) 
    { 
        this.DataForm.MoveCurrentToNext(); 
        this.DataForm.BeginEdit(); 
    } 
} 
protected override void MoveCurrentToPrevious() 
{ 
    if (this.DataForm != null) 
    { 
        this.DataForm.MoveCurrentToPrevious(); 
        this.DataForm.BeginEdit(); 
    } 
} 

Protected Overrides Sub MoveCurrentToNext() 
    If Me.DataForm IsNot Nothing Then 
        Me.DataForm.MoveCurrentToNext() 
        Me.DataForm.BeginEdit() 
    End If 
End Sub 
Protected Overrides Sub MoveCurrentToPrevious() 
    If Me.DataForm IsNot Nothing Then 
        Me.DataForm.MoveCurrentToPrevious() 
        Me.DataForm.BeginEdit() 
    End If 
End Sub 

CommitEdit and CancelEdit

A common requirement for data form is to add confirmation message boxes when CRUD operations are executed. Here we will do a similar thing with the CommitEdit/CancelEdit commands.

Example 5: Customizing CommitEdit and CancelEdit

• C#
• VB.NET

protected override void CommitEdit() 
{ 
    MessageBoxResult result = MessageBox.Show("Commit changes for the current edit item?", "CommitEdit confirmation", MessageBoxButton.OKCancel); 
    if (result == MessageBoxResult.OK) 
    { 
        if (this.DataForm != null && this.DataForm.ValidateItem()) 
        { 
            this.DataForm.CommitEdit(); 
        } 
    } 
} 
protected override void CancelEdit() 
{ 
    MessageBoxResult result = MessageBox.Show("Cancel changes for the current edit item?", "CancelEdit confirmation", MessageBoxButton.OKCancel); 
    if (result == MessageBoxResult.OK) 
    { 
        if (this.DataForm != null) 
        { 
            this.DataForm.CancelEdit(); 
        } 
    } 
} 

Protected Overrides Sub CommitEdit() 
    Dim result As MessageBoxResult = MessageBox.Show("Commit changes for the current edit item?", "CommitEdit confirmation", MessageBoxButton.OKCancel) 
    If result = MessageBoxResult.OK Then 
        If Me.DataForm IsNot Nothing AndAlso Me.DataForm.ValidateItem() Then 
            Me.DataForm.CommitEdit() 
        End If 
    End If 
End Sub 
Protected Overrides Sub CancelEdit() 
    Dim result As MessageBoxResult = MessageBox.Show("Cancel changes for the current edit item?", "CancelEdit confirmation", MessageBoxButton.OKCancel) 
    If result = MessageBoxResult.OK Then 
        If Me.DataForm IsNot Nothing Then 
            Me.DataForm.CancelEdit() 
        End If 
    End If 
End Sub 

Setting the Custom DataFormCommandProvider

The last thing to be done is to set the CommandProvider property of the RadDataForm to the newly-created CustomKeyboardCommandProvider class:

Example 6: Set the CommandProvider Property

• XAML

<Grid.Resources> 
    <my:CustomCommandProvider x:Key="CustomProvider"/> 
</Grid.Resources> 
<telerik:RadDataForm x:Name="RadDataForm1" 
             ItemsSource="{Binding Employees}"  
             CommandProvider="{StaticResource CustomProvider}"/> 

Example 6: Set the CommandProvider Property

• C#
• VB.NET

this.RadDataForm1.CommandProvider = new CustomCommandProvider(this.RadDataForm1); 

Me.RadDataForm1.CommandProvider = New CustomCommandProvider(Me.RadDataForm1) 

Executing Commands Manually

Using the RadDataFormCommands class, you can set a sequence of commands to be performed one after another. So, for example, you may easily handle the click event of a button, move to the next item and put it in edit mode. However, when invoking the commands in such a manner a second parameter should be added, pointing out the target UI Element as shown in Exapmle 7.

Example 7: Executing a sequence of commands

• C#
• VB.NET

private void Button1_Click(object sender, RoutedEventArgs e) 
{ 
    var moveToNextCommand = RadDataFormCommands.MoveCurrentToNext as RoutedUICommand; 
    var editCommand = RadDataFormCommands.BeginEdit as RoutedUICommand; 
    moveToNextCommand.Execute(null, this.DataForm); 
    editCommand.Execute(null, this.DataForm); 
} 

Private Sub Button1_Click(ByVal sender As Object, ByVal e As RoutedEventArgs) 
    Dim moveToNextCommand = TryCast(RadDataFormCommands.MoveCurrentToNext, RoutedUICommand) 
    Dim editCommand = TryCast(RadDataFormCommands.BeginEdit, RoutedUICommand) 
    moveToNextCommand.Execute(Nothing, Me.DataForm) 
    editCommand.Execute(Nothing, Me.DataForm) 
End Sub