You should try out this code:
<pre lang="cs">private void button1_Click(object sender, System.EventArgs e)
{
InputBoxResult test = InputBox.Show("Prompt" + "\n" + "DDDD" +
"Prompt" + "\n" + "DDDD" +
"Prompt" + "\n" + "DDDD" + "Prompt" + "\n" + "DDDD" +
"Prompt" + "\n" + "DDDD" +
"Prompt" + "\n" + "DDDD"
,"Title","Default",100,0);
if( test.ReturnCode == DialogResult.OK )
MessageBox.Show(test.Text);
}