What's the equivalent VB.NET syntax for anonymous types in a LINQ statement?

Question

I'm trying to translate some C# LINQ code into VB.NET and am stuck on how to declare an anonymous type in VB.NET.

.Select(ci => 
    new { CartItem = ci, 
          Discount = DiscountItems.FirstOrDefault(di => di.SKU == ci.SKU) }) 

How do you translate C#'s new { ... } syntax into VB.NET?

Solution 1

new { ... } becomes

New With { ... } in VB.NET,

or

New With {Key ... } if you want to use Key properties (which allows you to compare two anonymous type instances but does not allow the values of those properties to be changed).

So I'm guessing your statement would look like:

.Select(Function(ci) New With {Key _
    .CartItem = ci, _
    .Discount = DiscountItems.FirstOrDefault(Function(di) di.SKU = ci.SKU) _
})

Solution 2

C#:

new {name1 = "value1", name2 = "value2"}

VB equivalent:

New With {Key .name1 = "value1", Key .name2 = "value2"}

Also,

C#:

new {anotherObj.prop1, anotherObj.prop2}

VB equivalent:

New With {Key anotherObj.prop1, Key anotherObj.prop2}

Note: The Key keyword in VB equivalents is necessary. When you specify the Key in VB, the property becomes read-only and is checked in Equal method AND in C# all properties of anonymous types are read-only and are checked in Equal method.

See:

Anonymous Types (C# Programming Guide)

Anonymous Types (Visual Basic)

Comments

[Pat Migliaccio]

Thanks! Trying to write something so simple in VB is painstakingly hard when working regularly in C#.

[Darryl]

The Key keyword is indeed required if you want the exact same behavior as C#. Just to clarify, VB gives you some flexibility with anonymous types that C# doesn't provide. Any fields you don't precede with Key is read-write rather than read-only and is excluded from equality comparisons, which just might be exactly what you want.