asp.net mvc - Match any string starting with certain characters regex MVC DataAnnotations

Question

I new to Regular Expressions in MVC DataAnnotations. I have a form that has a field named Option. The option must start with CA-. I wrote the Regular Expression in different ways to validate this field and I can get it to work. I tried all this:

[RegularExpression(@"^CA-")]
[RegularExpression(@"/CA-/")]
[RegularExpression(@"^[C]+[A]+[-]")]
[RegularExpression(@"^CA-*")]

none of this work. What is wrong with my code? Thank you.

public class CA_OptionsMetadata
{
    [RegularExpression(@"^CA-", ErrorMessage = "The Option must start with CA-")]
    [Required(ErrorMessage = "Option is Required")]
    public string Option { get; set; }
    //public string Cap_LBS { get; set; }
    //public string Cap_KG { get; set; }
}

Answer 1

To match CA at the beginning of a string, use

@"^CA-.*$"

The main point is that the whole string should match (it is required by the RegularExpression), thus .*$ is important.

Regex explanation:

• ^ - start of string
• CA- - a literal CA- sequence of characters
• .* - zero or more characters other than a newline
• $ - end of string