Hi akhter,
Check this example. Now please take its reference and correct your code.
C#
private void btnChange_Click(object sender, EventArgs e)
{
string value = textBox1.Text;
List<char> letters = value.ToCharArray().Reverse().ToList();
textBox2.Text = string.Join("", letters);
}
VB.Net
Private Sub btnChange_Click(sender As System.Object, e As System.EventArgs) Handles btnChange.Click
Dim value As String = textBox1.Text
Dim letters As List(Of Char) = value.ToCharArray().Reverse().ToList()
textBox2.Text = String.Join("", letters)
End Sub
Screenshot