// This event handler creates a thread that calls a   // Windows Forms control in an unsafe way.  private void setTextUnsafeBtn_Click(   object sender,    EventArgs e)  {   this.demoThread =     new Thread(new ThreadStart(this.ThreadProcUnsafe));   this.demoThread.Start();  }  // This method is executed on the worker thread and makes  // an unsafe call on the TextBox control.  private void ThreadProcUnsafe()  {   this.textBox1.Text = "This text was set unsafely.";  }

// This event handler creates a thread that calls a   // Windows Forms control in a thread-safe way.  private void setTextSafeBtn_Click(   object sender,    EventArgs e)  {    this.demoThread =     new Thread(new ThreadStart(this.ThreadProcSafe));    this.demoThread.Start();  }  // This method is executed on the worker thread and makes  // a thread-safe call on the TextBox control.  private void ThreadProcSafe()  {   this.SetText("This text was set safely.");  }

using System;using System.ComponentModel;using System.Threading;using System.Windows.Forms;namespace CrossThreadDemo{ public class Form1 : Form {  // This delegate enables asynchronous calls for setting  // the text property on a TextBox control.  delegate void SetTextCallback(string text);  // This thread is used to demonstrate both thread-safe and  // unsafe ways to call a Windows Forms control.  private Thread demoThread = null;  // This BackgroundWorker is used to demonstrate the   // preferred way of performing asynchronous operations.  private BackgroundWorker backgroundWorker1;  private TextBox textBox1;  private Button setTextUnsafeBtn;  private Button setTextSafeBtn;  private Button setTextBackgroundWorkerBtn;  private System.ComponentModel.IContainer components = null;  public Form1()  {   InitializeComponent();  }  protected override void Dispose(bool disposing)  {   if (disposing && (components != null))   {    components.Dispose();   }   base.Dispose(disposing);  }  // This event handler creates a thread that calls a   // Windows Forms control in an unsafe way.  private void setTextUnsafeBtn_Click(   object sender,    EventArgs e)  {   this.demoThread =     new Thread(new ThreadStart(this.ThreadProcUnsafe));   this.demoThread.Start();  }  // This method is executed on the worker thread and makes  // an unsafe call on the TextBox control.  private void ThreadProcUnsafe()  {   this.textBox1.Text = "This text was set unsafely.";  }  // This event handler creates a thread that calls a   // Windows Forms control in a thread-safe way.  private void setTextSafeBtn_Click(   object sender,    EventArgs e)  {   this.demoThread =     new Thread(new ThreadStart(this.ThreadProcSafe));   this.demoThread.Start();  }  // This method is executed on the worker thread and makes  // a thread-safe call on the TextBox control.  private void ThreadProcSafe()  {   this.SetText("This text was set safely.");  }  // This method demonstrates a pattern for making thread-safe  // calls on a Windows Forms control.   //  // If the calling thread is different from the thread that  // created the TextBox control, this method creates a  // SetTextCallback and calls itself asynchronously using the  // Invoke method.  //  // If the calling thread is the same as the thread that created  // the TextBox control, the Text property is set directly.   private void SetText(string text)  {   // InvokeRequired required compares the thread ID of the   // calling thread to the thread ID of the creating thread.   // If these threads are different, it returns true.   if (this.textBox1.InvokeRequired)   {     SetTextCallback d = new SetTextCallback(SetText);    this.Invoke(d, new object[] { text });   }   else   {    this.textBox1.Text = text;   }  }  // This event handler starts the form's   // BackgroundWorker by calling RunWorkerAsync.  //  // The Text property of the TextBox control is set  // when the BackgroundWorker raises the RunWorkerCompleted  // event.  private void setTextBackgroundWorkerBtn_Click(   object sender,    EventArgs e)  {   this.backgroundWorker1.RunWorkerAsync();  }    // This event handler sets the Text property of the TextBox  // control. It is called on the thread that created the   // TextBox control, so the call is thread-safe.  //  // BackgroundWorker is the preferred way to perform asynchronous  // operations.  private void backgroundWorker1_RunWorkerCompleted(   object sender,    RunWorkerCompletedEventArgs e)  {   this.textBox1.Text =     "This text was set safely by BackgroundWorker.";  }  #region Windows Form Designer generated code  private void InitializeComponent()  {   this.textBox1 = new System.Windows.Forms.TextBox();   this.setTextUnsafeBtn = new System.Windows.Forms.Button();   this.setTextSafeBtn = new System.Windows.Forms.Button();   this.setTextBackgroundWorkerBtn = new System.Windows.Forms.Button();   this.backgroundWorker1 = new System.ComponentModel.BackgroundWorker();   this.SuspendLayout();   //    // textBox1   //    this.textBox1.Location = new System.Drawing.Point(12, 12);   this.textBox1.Name = "textBox1";   this.textBox1.Size = new System.Drawing.Size(240, 20);   this.textBox1.TabIndex = 0;   //    // setTextUnsafeBtn   //    this.setTextUnsafeBtn.Location = new System.Drawing.Point(15, 55);   this.setTextUnsafeBtn.Name = "setTextUnsafeBtn";   this.setTextUnsafeBtn.TabIndex = 1;   this.setTextUnsafeBtn.Text = "Unsafe Call";   this.setTextUnsafeBtn.Click += new System.EventHandler(this.setTextUnsafeBtn_Click);   //    // setTextSafeBtn   //    this.setTextSafeBtn.Location = new System.Drawing.Point(96, 55);   this.setTextSafeBtn.Name = "setTextSafeBtn";   this.setTextSafeBtn.TabIndex = 2;   this.setTextSafeBtn.Text = "Safe Call";   this.setTextSafeBtn.Click += new System.EventHandler(this.setTextSafeBtn_Click);   //    // setTextBackgroundWorkerBtn   //    this.setTextBackgroundWorkerBtn.Location = new System.Drawing.Point(177, 55);   this.setTextBackgroundWorkerBtn.Name = "setTextBackgroundWorkerBtn";   this.setTextBackgroundWorkerBtn.TabIndex = 3;   this.setTextBackgroundWorkerBtn.Text = "Safe BW Call";   this.setTextBackgroundWorkerBtn.Click += new System.EventHandler(this.setTextBackgroundWorkerBtn_Click);   //    // backgroundWorker1   //    this.backgroundWorker1.RunWorkerCompleted += new System.ComponentModel.RunWorkerCompletedEventHandler(this.backgroundWorker1_RunWorkerCompleted);   //    // Form1   //    this.ClientSize = new System.Drawing.Size(268, 96);   this.Controls.Add(this.setTextBackgroundWorkerBtn);   this.Controls.Add(this.setTextSafeBtn);   this.Controls.Add(this.setTextUnsafeBtn);   this.Controls.Add(this.textBox1);   this.Name = "Form1";   this.Text = "Form1";   this.ResumeLayout(false);   this.PerformLayout();  }  #endregion  [STAThread]  static void Main()  {   Application.EnableVisualStyles();   Application.Run(new Form1());  } }}