If you are developing an application in MVC C# use this code in your password model to make easy validation
[Required] [DataType(DataType.Password)] [StringLength(100, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 8)] [Display(Name = "Password")] [RegularExpression("^((?=.*?[A-Z])(?=.*?[a-z])(?=.*?[0-9])|(?=.*?[A-Z])(?=.*?[a-z])(?=.*?[^a-zA-Z0-9])|(?=.*?[A-Z])(?=.*?[0-9])(?=.*?[^a-zA-Z0-9])|(?=.*?[a-z])(?=.*?[0-9])(?=.*?[^a-zA-Z0-9])).{8,}$", ErrorMessage = "Passwords must be at least 8 characters and contain at 3 of 4 of the following: upper case (A-Z), lower case (a-z), number (0-9) and special character (e.g. !@#$%^&*)")] public string Password { get; set; }
This will impose following password policy
Passwords must be at least 8 characters
And
Satisfy any of 3 from 4 of the following:
- upper case (A-Z),
- lower case (a-z),
- number (0-9)
- special character (e.g. !@#$%^&*)