c# Is there a better way to validate user input [closed]

Question

I have the following code:

private void btnOK_Click(object sender, EventArgs e)
    {
        if (!string.IsNullOrEmpty(tbVendorName.Text))
        {
            VendorName = tbVendorName.Text;
            if (!string.IsNullOrEmpty(rtbVendorAddress.Text))
            {
                VendorAddress = rtbVendorAddress.Text;
                if (!string.IsNullOrEmpty(tbVendorEmail.Text))
                {
                    VendorEmail = tbVendorEmail.Text;
                    if (!string.IsNullOrEmpty(tbVendorWebsite.Text))
                    {
                        VendorWebsite = tbVendorWebsite.Text;
                        this.Close();
                    }
                    else
                    {
                        MessageBox.Show("Vendor Website Required");
                    }
                }
                else
                {
                    MessageBox.Show("Vendor email is required");
                }
            }
            else
            {
                MessageBox.Show("Vendor address is required");
            }
        }
        else
        {
            MessageBox.Show("Vendor name is required");
        }
    }

But it just looks horrible. Is there a better way? Or even an alternative methodology which makes the code more readable?

Answer 1

The better way is to master the MVVM pattern. There you could create a ViewModel and define all input data there:

class VendorViewModel
{
    [Required]
    public string Name { get; set; }

    public string Website { get; set; }

    [Regex("regex for email")]
    public string Email { get; set; }

    [MaxLength(160)]
    public string Address { get; set; }
}

Then the framework will show input errors (if any) after each textbox or any other input element. Enable property of the button will be automatically set according of all fields validated correctly.

Answer 2

Put it in a method and return from the method a boolean as to valid or not.

 private void btnOK_Click(object sender, EventArgs e)
{
    if(!Validate())
    {
        //Invalid
    }
    //Valid so set details
}

private bool Validate()
{
     if (!string.IsNullOrEmpty(tbVendorName.Text))
     {
          MessageBox.Show(...);
        return false;
     }

    return true;
}