Function Problem - Check empty textboxes

Hello, i've a problem with this function. Error = errorProvider

  public bool IsEmpty { get; set; }

public void CheckEmpty(List<TextBox> txt)
        {
            foreach (TextBox t in txt)
            {

                if (t.Text == string.Empty)
                {
                    IsEmpty = true;
                    error.SetError(t, "Error");
                }

                else
                {
                    error.Clear();

                }

            }

            if (IsEmpty == true)
            {
                MessageBox.Show("Eror!", "Error!", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }


        private void button2_Click(object sender, EventArgs e)
        {
            List<TextBox> txt = new List<TextBox>() { textBox1, textBox2 };
            CheckIsEmptyPart(txt);

        }

Now, when I write some in textBox1 and texBox2 - is ok - no error. When textbox1 and textbox2 is empty - is ok, shows up Error Text, but now when I write some in textboxes - Icons errordisappear and shows up again Error Text,although textboxes doesn't empty. How can Ichange thefunction thatwas ok?

Thanks