Instead of passing the textbox - or using ToString on a Text box - use the Text property.
If you use this:
TextBox myTextBox = new TextBox();
myTextBox.Text = "hello";
string s = myTextBox.ToString();
You will get "System.Windows.Forms.TextBox, Text: hello"
If you use this:
TextBox myTextBox = new TextBox();
myTextBox.Text = "hello";
string s = myTextBox.Text;
You will get "hello"