Question

I need to generate random string for my automated tests. I use the following Chinese custom class to do it.

public class UniqueIdGenerator
  {
    static public string GenerateUniqueId(int idLength)    // generates uniqueID for all fields (0-175 characters)
    {
      string uniqueID = "";
      string initialID = Guid.NewGuid().ToString().Remove(35);

      if (idLength <= 35)
      {
        uniqueID = Guid.NewGuid().ToString().Remove(idLength);
      }
      if (idLength > 35 & idLength <= 70)
      {
        uniqueID = initialID + Guid.NewGuid().ToString().Remove(idLength - 35);
      }
      if (idLength > 70 & idLength <= 105)
      {
        uniqueID = initialID + initialID + Guid.NewGuid().ToString().Remove(idLength - 70);
      }
      if (idLength > 105 & idLength <= 140)
      {
        uniqueID = initialID + initialID + initialID + Guid.NewGuid().ToString().Remove(idLength - 105);
      }
      if (idLength > 140 & idLength <= 175)
      {
        uniqueID = initialID + initialID + initialID + initialID + Guid.NewGuid().ToString().Remove(idLength - 140);
      }

      return uniqueID;
    }

How can I simplify it to use for any natural number?

Answer 1

Try the following:

var builder = new StringBuilder();
while(builder.Length < idLength) 
{
  builder.Append(Guid.NewGuid().ToString());
}
return builder.ToString(0, idLength);

If all you require is a method capable of generating garbage for testing purposes, then perhaps the following would be more suitable:

private static Random Random = new Random();
public static string GenerateRandomString(int length, string characterSet = "abcdefghijklmnopqrstuvwxyzABCDDEFGHIJKLMNOPQRSTUVWXYZ")
{
    var builder = new StringBuilder();
    while(builder.Length < length) 
    {
        builder.Append(characterSet.Chars[Random.Next(characterSet.Length)]);
    }
    return builder.ToString();
}

As an aside, when randomising values for tests, I prefer to still give my properties descriptive names as I find that the fail messages are generally far more helpful. I use an extension method for this purpose:

private static Random Random = new Random();
public static string Randomise(this string value)
{
  return value + Random.Next();
}

Which is the useable in my tests like so:

var customer = new Customer { Id = "CustomerId".Randomise() };

This may not be applicable in this case, since a string of a given length is required, however it does save a bit of time if/when a test fails.