GetValueOrDefaultMany VB.NET programs use the Dictionary type, and accessing values is nearly always needed. The GetValueOrDefault function provides an easy and safe way to do this.
With this function, we get the default value (not an error) if the key is not found. This often allows to us omit If-checks in our programs, making them clearer.
It is important to understand the use of the GetValueOrDefault function a complete VB.NET program. We must first create a Dictionary to test this function.
Dictionary and populate it with 2 keys and values. We have String keys, and Integer values.GetValueOrDefault on a key that exists. The correct value (10) is returned.Module Module1
Sub Main()
' Part 1: create Dictionary.
Dim animals As Dictionary(Of String, Integer) = New Dictionary(Of String, Integer)
animals.Add("cat", 10)
animals.Add("dog", 20)
' Part 2: use GetValueOrDefault.
Dim result = animals.GetValueOrDefault("cat")
Console.WriteLine($"cat = {result}")
' Part 3: key not found.
result = animals.GetValueOrDefault("computer")
Console.WriteLine($"computer = {result}")
End Sub
End Modulecat = 10
computer = 0String valuesWhat happens when we use GetValueOrDefault on a Dictionary with String values? In VB.NET the default value for a String is Nothing.
Dictionary, and we leave it empty because we are just testing nonexistent values in this program.String can be returned.GetValueOrDefault for no String value, we can use the IsNothing function.IsNothing.Module Module1
Sub Main()
' Part 1: create an empty Dictionary with string values.
Dim ids = New Dictionary(Of String, String)
' Part 2: get key that is not found.
Dim result = ids.GetValueOrDefault("missing")
' Part 3: we can test for Nothing with IsNothing.
If IsNothing(result)
Console.WriteLine("OK")
End If
End Sub
End ModuleOKA simple function that makes Dictionary collections easier to use is worth knowing about. GetValueOrDefault can replace many uses of TryGetValue and the indexer.