Question

As a non-.NET programmer I’m looking for the .NET equivalent of the old Visual Basic function left(string, length). It was lazy in that it worked for any length string. As expected, left("foobar", 3) = "foo" while, most helpfully, left("f", 3) = "f".

In .NET string.Substring(index, length) throws exceptions for everything out of range. In Java I always had the Apache-Commons lang.StringUtils handy. In Google I don’t get very far searching for string functions.

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@Noldorin – Wow, thank you for your VB.NET extensions! My first encounter, although it took me several seconds to do the same in C#:

public static class Utils
{
    public static string Left(this string str, int length)
    {
        return str.Substring(0, Math.Min(length, str.Length));
    }
}

Note the static class and method as well as the this keyword. Yes, they are as simple to invoke as "foobar".Left(3). See also C# extensions on MSDN.

Answer 1

Here’s an extension method that will do the job.

<System.Runtime.CompilerServices.Extension()> _
Public Function Left(ByVal str As String, ByVal length As Integer) As String
    Return str.Substring(0, Math.Min(str.Length, length))
End Function

This means you can use it just like the old VB Left function (i.e. Left("foobar", 3) ) or using the newer VB.NET syntax, i.e.

Dim foo = "f".Left(3) ' foo = "f"
Dim bar = "bar123".Left(3) ' bar = "bar"