SebiBasti

using System;

public class Class1 { // find a more descriptive class name
    public static bool IsFormat(string str, string f) // rename f to format and rename to IsFormatValid
    {
        var allowedDict = new Dictionary<string, bool>() // use an Array instead of a Dictionary
        {
            { "number",true},
            { "date",true},
            { "timespan",true}