textbox textwriter impl

public class TextBoxTextWritter : TextWriter {
    public override Encoding Encoding => Encoding.Unicode;

    private TextBox textBox;
    public TextBox TextBox { get => this.textBox; }

    public TextBoxTextWritter(TextBox box) {
        this.textBox = box;
    }

    public override void Write(char value) {
        this.textBox.Text += value;
    }

    public override void Write(char[] buffer, int index, int count) {
        this.textBox.Text += new StringBuilder(count - index).Append(buffer, index, count).ToString();
    }
}