Array For Func Lambda Nothing String Length String StartsWith

`Array.Find`

The VB.NET Array.Find Function is available for all arrays. It searches an array. It applies a Predicate method we specify.

The Predicate we pass to Array.Find indicates whether an element matches or not. It returns a Boolean. We demonstrate Array.Find.

An example

First, we use Array.Find with two arguments. The first argument is the array we are searching. And the second is the Predicate definition.

Info We use the lambda expression syntax to specify the predicates. We handle String elements.

Next We use the StartsWith Function to test prefixes. We use the Length property to access character counts.

Then We also apply the FindAll Function. This is similar to Find, but it returns an array of all the elements found.

Info Find returns only one element. If no matches are found, Nothing is returned.

Module Module1
    Sub Main()

        ' Input array.
        Dim arr() As String = {"cat", "dog", "carrot", "bird"}

        ' Find element starting with "car".
        Dim value1 As String = Array.Find(arr, Function(x) (x.StartsWith("car")))
        Console.WriteLine(value1)

        ' Find element of length 3.
        Dim value2 As String = Array.Find(arr, Function(x) (x.Length = 3))
        Console.WriteLine(value2)

        ' Find all elements of length 4 or less.
        Dim arr2() As String = Array.FindAll(arr, Function(x) (x.Length <= 4))
        Console.WriteLine(String.Join(",", arr2))

    End Sub
End Modulecarrot
cat
cat,dog,bird

Notes, lambdas

We use the Function keyword to specify a lambda. The first part is the argument to the Function, and the second is the expression that the Function evaluates and returns.

Summary

Arrays can be searched with loops. This often results in more complex code—we must manage arrays, elements and indexes. With Find and FindAll, we eliminate these forms of complexity.