TextBox einer anderen Form per Button befüllen

StartForm-Name.Show()

StartForm-Name.TextBox-Name.Text = "DeinText"  

Me.Close()

namespace MyForms {
    static class Program {
        public static string mystring;
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main(string args) {
            if (args.Length == 1) {
                mystring = args;
            }
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
        }
    }
}

namespace MyForms {
    public partial class Form1 : Form {
        public Form1() {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e) {
            if (Program.mystring != "") {  
                textBox1.Text = Program.mystring;
            }
        }

        private void btnOpenForm2_Click(object sender, EventArgs e) {
            Form2 f = new Form2(textBox1.Text);
            f.ShowDialog(this);
        }
    }
}

namespace MyForms {
    public partial class Form2 : Form {
        string s;
        public Form2() {
            InitializeComponent();
        }
        public Form2(string s) {
            InitializeComponent();
            this.s = s;
        }

        private void button1_Click(object sender, EventArgs e) {
            Process.Start(Application.ExecutablePath, s);
            Application.Exit();
        }
    }
}