I have in my C# program textBox
I need that when the program start, the focus will be on the textBox
I try this on Form_Load:
MyTextBox.Focus
Set Tabstop to True and TabIndex to the minimum to the control on which you need focus.
e.g. If you have 2 TextBoxes : TextBox1 and TextBox2, set Tabstop to True for both and TabIndex to 0 and 1 respectively. When the form loads, the focus will be on TextBox1 and on the press of 'Tab' key, the focus will move to TextBox2.