SimpleButton.CommandParameter Property

Specifies the parameter passed to the Command.

Namespace: DevExpress.XamarinForms.Editors

Assembly: DevExpress.XamarinForms.Editors.dll

NuGet Package: DevExpress.XamarinForms.Editors

Declaration

public object CommandParameter { get; set; }

Property Value

Type	Description
Object	A parameter object.

Remarks

Use CommandParameter property with Command to pass data to the command.

Example

This example shows how to create a custom command with a parameter and execute it when a user taps the button.

1. In a view model, create a command that implements the ICommand interface:

   C#

   using System.ComponentModel;
   using System.Windows.Input;
   
   namespace TestICommand.ViewModels {
       public class ValidationCommand : ICommand {
           public event EventHandler CanExecuteChanged;
   
           MainViewModel viewModel;
           public ValidationCommand(MainViewModel viewModel) {
               this.viewModel = viewModel;
           }
   
           public bool CanExecute(object Login) {
               if (string.IsNullOrEmpty((string)Login) || Login == null) {
                   viewModel.ValidationResultText = "Login cannot be empty";
                   viewModel.TextHasError = true;
                   return false;
               }
               viewModel.ValidationResultText = "";
               viewModel.TextHasError = false;
               return true;            
           }
   
           public void Execute(object Login) {
               viewModel.ValidationResultText = $"Login {Login} is correct";
           }
       }
   
       public class MainViewModel : INotifyPropertyChanged {
           public MainViewModel() {
               buttonCommand = new ValidationCommand(this);
           }
   
           ICommand buttonCommand = null;
           public ICommand ButtonCommand {
               get { return buttonCommand; }
               set { 
                   if (buttonCommand != value) {
                       buttonCommand = value;
                       OnPropertyChanged("ButtonCommand");
                   }
               }
           }
   
           public event PropertyChangedEventHandler PropertyChanged;
           protected void OnPropertyChanged(string name) {
               PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
           }
   
           bool textHasError = false;
           public bool TextHasError {
               get { return textHasError; }
               set { 
                   if (textHasError != value) {
                       textHasError = value;
                       OnPropertyChanged("TextHasError");
                   }
               }
           }
   
           string validationResultText = "";
           public string ValidationResultText {
               get { return validationResultText; }
               set { 
                   validationResultText = value;
                   OnPropertyChanged("ValidationResultText");
               }
           }
       }
   }
   

2. Bind the specified command to the Command property and define the CommandParameter value:

   XAML

   <ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
           xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
           xmlns:local="clr-namespace:TestICommand"
           xmlns:vm="clr-namespace:TestICommand.ViewModels"
           x:Class="TestICommand.MainPage"
           xmlns:dxe="http://schemas.devexpress.com/xamarin/2014/forms/editors">
       <ContentPage.BindingContext>
           <vm:MainViewModel/>
       </ContentPage.BindingContext>
       <StackLayout>
           <dxe:TextEdit x:Name="TextEditor" 
                         HasError="{Binding TextHasError}"/>
   
           <dxe:SimpleButton x:Name="MyButton" 
                             Text="Check"
                             Command="{Binding ButtonCommand}"
                             CommandParameter="{Binding Source={x:Reference TextEditor}, Path=Text}"/>
   
           <Label Text="{Binding ValidationResultText}"
                  HorizontalOptions="Center"/>    
       </StackLayout>
   </ContentPage>