check content of string input

Question

How can I check if my input is a particular kind of string. So no numeric, no \"/\",...

Answer 1

It's not entirely clear what you want, but you can probably do it with a regular expression. For example to check that your string contains only letters in a-z or A-Z you can do this:

string s = "dasglakgsklg";
if (Regex.IsMatch(s, "^[a-z]+$", RegexOptions.IgnoreCase))
{
    Console.WriteLine("Only letters in a-z.");
}
else
{
    // Not only letters in a-z.
}

If you also want to allow spaces, underscores, or other characters simply add them between the square brackets in the regular expression. Note that some characters have a special meaning inside regular expression character classes and need to be escaped with a backslash.

You can also use \p{L} instead of [a-z] to match any Unicode character that is considered to be a letter, including letters in foreign alphabets.

Answer 2

Something like this (have not tested) may fit your (vague) requirement.

if (input is string)
{
    // test for legal characters?
    string pattern = "^[A-Za-z]+$";
    if (Regex.IsMatch(input, pattern))
    {
         // legal string? do something 
    }

    // or
    if (input.Any(c => !char.IsLetter(c)))
    {
         // NOT legal string 
    }
}

Answer 3

Well, to check that an input is actually an object of type System.String, you can simply do:

bool IsString(object value)
{
    return value is string;
}

To check that a string contains only letters, you could do something like this:

bool IsAllAlphabetic(string value)
{
    foreach (char c in value)
    {
        if (!char.IsLetter(c))
            return false;
    }

    return true;
}

If you wanted to combine these, you could do so:

bool IsAlphabeticString(object value)
{
    string str = value as string;
    return str != null && IsAllAlphabetic(str);
}

Answer 4

using System.Linq;
...

bool onlyAlphas = s.All(c => (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z'));

Answer 5

If you mean "is the string completely letters", you could do:

string myString = "RandomStringOfLetters";
bool allLetters = myString.All( c => Char.IsLetter(c) );

This is based on LINQ and the Char.IsLetter method.