how to check all textbox on click btnsave

how to check all textbox on click btnsave if there is no empty text box do something else message error that you have to need to fill empty textbox frist
i try this code

foreach (Control c in this.Controls)
{
if (c is TextBox)
{
TextBox textBox = c as TextBox;
if (textBox.Text == string.Empty)
{
textbox.text="please fill your empty textbox ";
}

else
{
// if my textbox all are fill i put my code to save data in datebase here
}
}
}



i try this code but it do nothing ????