• Article

LocalMessageSender.SendAsync Method (String, Object)

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Sends the specified messages to the configured receiver asynchronously.

Namespace:  System.Windows.Messaging
Assembly:  System.Windows (in System.Windows.dll)

Syntax

'Declaration
<SecuritySafeCriticalAttribute> _
Public Sub SendAsync ( _
    message As String, _
    userState As Object _
)

[SecuritySafeCriticalAttribute]
public void SendAsync(
    string message,
    Object userState
)

Parameters

  • userState
    Type: System.Object
    A unique user-state object that functions as a task ID for the message transfer.

Exceptions

Exception Condition
ArgumentNullException

message is nulla null reference (Nothing in Visual Basic).
ArgumentException

message is longer than 40,960 characters.

Remarks

You can send messages up to 40 kilobytes long.

When you call this method, the MessageReceived event occurs for the LocalMessageReceiver that corresponds to the ReceiverName and ReceiverDomain settings. Then, the SendCompleted event occurs, regardless of whether the message was successfully sent. You can retrieve the userState object in the SendCompleted event handler in order to identify the message.

For more information, see Communication Between Local Silverlight-Based Applications.

Examples

The following code example demonstrates how to use this method. This example is part of a larger example available in How to: Implement Communication Between Local Silverlight-Based Applications.

Imports System
Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Messaging

Partial Public Class Sender
    Inherits UserControl

    Private messageSender As LocalMessageSender

    Public Sub New()

        InitializeComponent()
        UpdateButton()
        messageSender = New LocalMessageSender( _
            "receiver", LocalMessageSender.Global)
        AddHandler messageSender.SendCompleted, _
            AddressOf sender_SendCompleted
        SendMessage("message from Sender constructor")

    End Sub

    Private clickNumber As Integer = 1

    Private Sub UpdateButton()
        button.Content = "send message 'click " & clickNumber & "'"
    End Sub

    Private Sub Button_Click(ByVal sender As Object, _
        ByVal e As RoutedEventArgs)

        SendMessage("click " & clickNumber)
        clickNumber += 1
        UpdateButton()

    End Sub

    Private Const MAX_ATTEMPTS As Integer = 10000
    Private attempt As Integer = 1

    Private Sub SendMessage(ByVal message As String)
        messageSender.SendAsync(message, attempt)
    End Sub

    Private Sub sender_SendCompleted(ByVal sender As Object, _
        ByVal e As SendCompletedEventArgs)

        If e.Error IsNot Nothing Then

            LogError(e)
            attempt += 1
            If attempt > MAX_ATTEMPTS Then
                output.Text = "Could not send message."
                Return
            End If
            SendMessage(e.Message)
            Return

        End If

        output.Text = _
            "Message: " & e.Message & Environment.NewLine & _
            "Attempt " & CType(e.UserState, Integer) & _
            " completed." & Environment.NewLine & _
            "Response: " & e.Response & Environment.NewLine & _
            "ReceiverName: " & e.ReceiverName & Environment.NewLine & _
            "ReceiverDomain: " & e.ReceiverDomain

        ' Reset attempt counter.
        attempt = 1

    End Sub

    Private Sub LogError(ByVal e As SendCompletedEventArgs)
        System.Diagnostics.Debug.WriteLine( _
            "Attempt number {0}: {1}: {2}", CType(e.UserState, Integer), _
            e.Error.GetType().ToString(), e.Error.Message)
    End Sub

End Class

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Messaging;

namespace SendingApplication
{
    public partial class Sender : UserControl
    {
        private LocalMessageSender messageSender;

        public Sender()
        {
            InitializeComponent();
            UpdateButton();
            messageSender = new LocalMessageSender(
                "receiver", LocalMessageSender.Global);
            messageSender.SendCompleted += sender_SendCompleted;
            SendMessage("message from Sender constructor");
        }

        private int clickNumber = 1;

        private void UpdateButton()
        {
            button.Content = "send message 'click " + clickNumber + "'";
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            SendMessage("click " + clickNumber);
            clickNumber++;
            UpdateButton();
        }

        private const int MAX_ATTEMPTS = 10000;
        private int attempt = 1;

        private void SendMessage(string message)
        {
            messageSender.SendAsync(message, attempt);
        }

        private void sender_SendCompleted(object sender, SendCompletedEventArgs e)
        {
            if (e.Error != null)
            {
                LogError(e);
                attempt++;
                if (attempt > MAX_ATTEMPTS)
                {
                    output.Text = "Could not send message.";
                    return;
                }
                SendMessage(e.Message);
                return;
            }

            output.Text =
                "Message: " + e.Message + Environment.NewLine +
                "Attempt " + (int)e.UserState + 
                " completed." + Environment.NewLine +
                "Response: " + e.Response + Environment.NewLine +
                "ReceiverName: " + e.ReceiverName + Environment.NewLine + 
                "ReceiverDomain: " + e.ReceiverDomain;

            // Reset attempt counter.
            attempt = 1;
        }

        private void LogError(SendCompletedEventArgs e)
        {
            System.Diagnostics.Debug.WriteLine(
                "Attempt number {0}: {1}: {2}", (int)e.UserState, 
                e.Error.GetType().ToString(), e.Error.Message);
        }

    }
}

Version Information

Silverlight

Supported in: 5, 4, 3

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.