if (String.IsNullOrWhiteSpace(textbox.Text)) { errorProvider1.show(textbox, "plese enter your name"); }
if (textbox.Text.Trim() == "") { errorProvider1.show(textbox, "plese enter your name"); }
if (textBox1.Text.Trim()==string.Empty) { errorProvider1.show(textbox,"plese enter your name"); }
var
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