Vb.Net Equivalent to C# Var Keyword

The equivalent for var keyword in Vb.Net

Just use Dim without a type designator.

Dim result = loginForm.ShowDialog()

What is the VB.NET equivalent of the C# “var” keyword?

Like this:

Dim myVar = 3

You'll also need

Option Infer On

(At the top of the file or in project settings)

See "Local Type Inference"

Translating C# var to VB.net

Just skip the type altogether:

For Each obj In objs

You can read more about Local Type Inference in VB.NET on MSDN: Local Type Inference (Visual Basic)

Is there a VB.net equivalent for C# out var

If I understand the intent of this question correctly, it is not asking about the exact syntax for passing by-reference parameters (a feature that VB.NET has always supported), but rather whether it is possible to declare a variable inline with the parameter list for a method call, as in the C# feature provided from C# 7 and later.

As such, the previously-proposed duplicate does not seem to address this question. That question was asking about a VB.NET-supported distinction between by-reference parameters that don't need to be initialized before passing and by-reference parameters that do, i.e. out vs. ref.

This question is asking about something else entirely.

Unfortunately, VB.NET does not provide a syntax that would allow local variables to be declared inline with a method call. Further, while there are several open Github issues that ask for this feature (see e.g. #60, #159, and #331), it appears unlikely that it would ever be added. Per a blog post from March 11, 2020, Microsoft has stated that "Going forward, we do not plan to evolve Visual Basic as a language". Presumably, new additions to the language syntax would fall under the category of "evolving the language", so method-call-inlined variable declarations would be ruled out.

See also Microsoft Plots the End of Visual Basic for additional context.

Sorry about that. :(

Is there a VB.NET equivalent of C# out parameters?

No, there is no equivalent of the out keyword in VB.

However, VB does automatically initialise all local variables in a method, so you can use ByRef without needing to explicitly initialise the variable first.

Example:

Sub Main()
  Dim y As Integer
  Test(y)
End Sub

Sub Test(ByRef x As Integer)
  x = 42
End Sub

(If you examine code in the framework (for example Double.TryParse), you may see the <OutAttribute> added to parameters, but that only makes a difference when the call is marshalled for COM interop or platform invoke.)

Is VB's Dim the same as C#'s var?

That depends if Option Infer is specified. Normally, the following are equivalent:

'VB.Net
Dim myVar
Dim myString = "Hello world!"
Dim myString2 As String = "Hello world!"

//C#
object myVar;
object myString = "Hello world!"; //Notice type is object, *not* string!
string myString2 = "Hello world!";

However, with Option Infer enabled, Dim becomes more like var when the variable is initialized on the same line:

'VB.Net
Option Infer On
Dim myVar
Dim myString = "Hello!"

//C#
object myVar;
var myString = "Hello!"; //Or the equivalent:  string myString = "Hello!";

Note that this can lead to some confusion because suddenly initializing a variable at the point of declaration means something different from initializing it later:

'VB.Net
Option Infer On
Dim myVar1
myVar1 = 10
Dim myVar2 = 10

myVar1 = New MyClass() 'Legal
myVar2 = New MyClass() 'Illegal! - Value of type 'MyClass' cannot be converted to 'Integer'

This can be fixed by enabling Option Strict, which (among other things) forces all variables to be given a type (implicitly or not) at the time of declaration.

What is the VB.NET equivalent of the C# is keyword?

Try the following

if TypeOf x Is IFoo Then 
  ...

How to convert Var from C# to VB?

For Each v In empInfo

To get VB to infer variable types, just omit the As clause, e.g.

Dim a = b + c

NOTE: This will only work when Option Infer is On. When Option Infer is Off, then variables without type specifiers will default to Object instead.

Equivalent of var in Visual Basic to use in For Each Loop

You would just use:

For Each item In removeRows
    two.ImportRow(item)
Next

The As datatype specification in VB is optional. See For Each documentation for details.

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