Writing to a TextBox from another thread? [duplicate]

On your MainForm make a function to set the textbox the checks the InvokeRequired

public void AppendTextBox(string value)
{
    if (InvokeRequired)
    {
        this.Invoke(new Action<string>(AppendTextBox), new object[] {value});
        return;
    }
    ActiveForm.Text += value;
}

although in your static method you can’t just call.

WindowsFormsApplication1.Form1.AppendTextBox("hi. ");

you have to have a static reference to the Form1 somewhere, but this isn’t really recommended or necessary, can you just make your SampleFunction not static if so then you can just call

AppendTextBox("hi. ");

It will append on a differnt thread and get marshalled to the UI using the Invoke call if required.

Full Sample

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        new Thread(SampleFunction).Start();
    }

    public void AppendTextBox(string value)
    {
        if (InvokeRequired)
        {
            this.Invoke(new Action<string>(AppendTextBox), new object[] {value});
            return;
        }
        textBox1.Text += value;
    }

    void SampleFunction()
    {
        // Gets executed on a seperate thread and 
        // doesn't block the UI while sleeping
        for(int i = 0; i<5; i++)
        {
            AppendTextBox("hi.  ");
            Thread.Sleep(1000);
        }
    }
}