`StartsWith`, `EndsWith`

In VB.NET StartsWith tests the first part of a String. It checks whether one String starts with the characters in another. EndsWith checks the last characters.

Some info

StartsWith is often useful. StartsWith supports the StringComparison.OrdinalIgnoreCase argument, which makes it case-insensitive. Without this argument, it is case-sensitive.

An example

Here we use StartsWith. This call is case-sensitive. We pass the StringComparison.OrdinalIgnoreCase enumerated constant. This makes "D" equal to "d" so StartsWith returns True.

Finally We show that StartsWith can also return False if the first String does not actually start with the second String.

Tip This logic is commonly needed in programs. We do not need to develop custom loops.

Module Module1
    Sub Main()
        Dim value As String = "Dot Net Perls"

        ' Use StartsWith.
        If value.StartsWith("Dot") Then
            Console.WriteLine(1)
        End If

        ' Use StartsWith ignoring case.
        If value.StartsWith("dot", StringComparison.OrdinalIgnoreCase) Then
            Console.WriteLine(2)
        End If

        ' It can return False.
        Console.WriteLine(value.StartsWith("Net"))
    End Sub
End Module1
2
False

Test chars

There is another way to check the first characters of a String. It is typically much faster. We test the Length of a String and then check characters by their indexes.

Tip The two If-statements shown here will always evaluate to the same truth value.

Module Module1
    Sub Main()
        Dim value As String = "cat"

        ' You could use StartsWith...
        If value.StartsWith("c") Then
            Console.WriteLine(1)
        End If

        ' Or you could check the character yourself.
        If value.Length >= 1 And value(0) = "c" Then
            Console.WriteLine(2)
        End If
    End Sub
End Module1
2

`EndsWith`

This tests the end part of a String. With it we specify a String that is then tested against the end characters of the first String.

And If they match it returns true. This Function is commonly useful in VB.NET programs that process text.

Here Let's get started with this VB.NET program. We use a String containing the address of this web site.

Detail We use the For-Each loop construct to loop through all the possible extensions and then use EndsWith on the first String.

Module Module1
    Sub Main()
        Dim value As String = "http://www.dotnetperls.com"
        Dim array() As String = {".net", ".org", ".edu", ".com"}

        For Each element As String In array
            If value.EndsWith(element) Then
                Console.WriteLine(element)
            End If
        Next
    End Sub
End Module
.com

`StringComparison`

You can pass a StringComparison enum as the second argument. The two most useful options are probably StringComparison.Ordinal and StringComparison.OrdinalIgnoreCase.

Detail This means letters are treated exactly as they are stored (as numbers).

Detail This means uppercase and lowercase letters are considered equal (meaning "A" equals "a").

A summary

We looked at the StartsWith and EndsWith methods. EndsWith is excellent for testing to see whether a String happens to start (or end) with another String.

StartsWith, EndsWith