Select Case is a VB.NET selection statement. It quickly matches the value of a variable with a set of constants in a VB.NET program. With Select Case we specify the variable and the individual Cases it may have.
To create a new Select Case statement, type Select and then press tab. Then, edit the variable name to be appropriate for your program. We read a line from the Console, call Integer.Parse on it, and then Select it from a set of cases.Integer.Parse
Program that uses Select Case: VB.NET Module Module1 Sub Main() Dim value As Integer = Integer.Parse(Console.ReadLine()) Select Case value Case 1 Console.WriteLine("You typed one") Case 2 Console.WriteLine("You typed two") Case 5 Console.WriteLine("You typed five") Case Else Console.WriteLine("You typed something else") End Select End Sub End Module Output 2 You typed two
The Select Case statement is implemented with the switch opcode in the intermediate language. This is the same implementation as the switch keyword from the C# language. With this opcode, Select Case can be faster than an If-statement.
Performance of Select Case is highly dependent on both the cases and the data in your program. If you have 1000 cases and one is most common, the fastest thing to do would be just test for the most common one first with an If-statement.
If the frequency of all cases is equally distributed, and the cases are close together in numeric value, then a Select Case is better. The performance difference in most situations is small.
Tip: It is often the best approach to just use whatever syntax form is clearest.
The Select Case statement in the VB.NET language provides an optimized way of selecting from several constant cases. This special syntax form can be used to test a variable against several constant values.
Note: Its performance is dependent on several factors. It may be slower or faster than If-statements.