Checking whether textboxes have data
Why so complicated? 

One possible approach is:

var f = new Form();
if (f.Controls.OfType&lt;TextBox&gt;().Any(x =&gt; string.IsNullOrWhiteSpace(x.Text)))
{
    /*your stuff*/
}


A second approach is:

var TextBox1 = new TextBox();
var TextBox2 = new TextBox();

var textboxes = new[] { TextBox1, TextBox2 };
if (textboxes.Any(x =&gt; string.IsNullOrWhiteSpace(x.Text)))
{
    /*your stuff*/
}