CODEWITHSUNDEEP
c#winformserrorprovider
LukeBorg
LukeBorg

Reputation: 33

Error Providers

I am trying to apply error providers to a text box,

The user cannot enter more than 25 characters The textbox cannot be left blank

private void txtNameandSurn_TextChanged(object sender, EventArgs e)
{
    txtNameandSurn.MaxLength = 25;

    if (txtNameandSurn.Text == "")
    {
        txtNameandSurn.BackColor = Color.White;
        errorProvider1.SetError(txtNameandSurn, "Cannot be blank!");
    }
    else
    {
        txtNameandSurn.BackColor = Color.Red;
        errorProvider1.SetError(txtNameandSurn, "");
    }

    if (txtNameandSurn.Text.Length >= txtNameandSurn.MaxLength)
    {
        errorProvider1.SetError(txtNameandSurn, "Cannot input more than 25 characters!");
    }
    else if (txtNameandSurn.Text.Length < txtNameandSurn.MaxLength)
    {
        errorProvider1.SetError(txtNameandSurn, "");
    }
}

The issue I have is with the character input, the error provider shows up but when i press another key the icon for the errorprovider disappears but the character is not inputted which is good. How do I keep the error provider icon showing?

Upvotes: 0

Views: 218

Answers (2)

Kevin Buchan
Kevin Buchan

Reputation: 2868

For great readability and flexibility for adding new rules, I prefer this syntax. Note that this also lends itself to creating reusable sets of rules for specific data types. This untested code should solve your problem with the errorProvider, if I understood it.

    class Rule 
    { 
        public Func<string, bool> Test { get; set; }
        public string Message { get; set; }
    }

    private void txtNameandSurn_TextChanged(object sender, EventArgs e)
    {
        var rules = new List<Rule>()
        {
            new Rule() { Test = s => !String.IsNullOrEmpty(s), Message="String cannot be blank." },
            new Rule() { Test = s => (s.Length <= txtNameandSurn.MaxLength), Message="String cannot be longer than " + txtNameandSurn.MaxLength },
            new Rule() { Test = s => !s.Contains("#"), Message = "String cannot contain a hash character." }
        };

        var isValid = rules.All(r => r.Test(txtNameandSurn.Text));

        string[] message;
        if (!isValid)
        {
            message = rules.Where(r => r.Test(txtNameandSurn.Text) == false).Select(r => r.Message);
        }

        errorProvider1.SetError((message.Length > 0) ? (string.Join(';', message)) : "");
    }

Upvotes: 1

Abbas
Abbas

Reputation: 14432

You should rewrite your conditions in a logical manner. Every case where there is not a correct input should have it's definition and have the correct error set. In the other case (input is correct), remove the error. Simplified it should look like this:

if (String.IsNullOrEmpty(textBox1.Text))
{
    errorProvider1.SetError(textBox1, "Cannot be blank!");
}
else if(textBox1.Text.Length >= textBox1.MaxLength)
{
    errorProvider1.SetError(textBox1, "Cannot input more than 25 characters!");
}
else
{
    errorProvider1.SetError(textBox1, "");
}

This way, you can add more conditions easiliy. If you want for example that the tekst doesn't contain a #, simply add following statement:

if(textBox1.Contains("#"))
{
    errorProvider1.SetError(textBox1, "Cannot contain a '#'!");
}

Upvotes: 1

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