Check if TextBox is empty and return MessageBox?

Question

I made this statement to check if TextBox is empty, but the MessageBox always shows up wether the TextBox is empty or not.

    private void NextButton_Click         


        

Answer 1

Well, you are clearing the textbox right before you check if it's empty

/* !! This clears the textbox BEFORE you check if it's empty */
MaterialTextBox.Clear();

HoursNumericUpDown.Value = HoursNumericUpDown.Minimum;
MarkNumericUpDown.Value = MarkNumericUpDown.Minimum;

if (String.IsNullOrEmpty(MaterialTextBox.Text))
{
        MessageBox.Show("Enter Material Name Please.", "Error", MessageBoxButtons.OK,    MessageBoxIcon.Warning);
            //dataGridView1.Rows.Clear();
}

Answer 2

For multiple text boxes - add them into a list and show all errors into 1 messagebox.

// Append errors into 1 Message Box      

 List<string> errors = new List<string>();   

 if (string.IsNullOrEmpty(textBox1.Text))
    {
        errors.Add("User");
    }

    if (string.IsNullOrEmpty(textBox2.Text))
    {
        errors.Add("Document Ref Code");
    }

    if (errors.Count > 0)
    {
        errors.Insert(0, "The following fields are empty:");
        string message = string.Join(Environment.NewLine, errors);
        MessageBox.Show(message, "errors", MessageBoxButtons.OK, MessageBoxIcon.Warning);
        return;
    }