C # differences between the anonymous type and the VB anonymous type

1. Anonymous type in C #

The anonymous type is a new feature introduced in C #3.0 (framework3.5. As the name implies, an anonymous type is an object without a type name, which inherits directly from the object.

The C # anonymous type can be defined in two ways:

// 1. directly declare the Member and initialize func <int, int> fun = x => x + 1; var ann1 = new {A = "str ", B = new object (), c = fun // C # You can use a delegate, but you cannot assign a Lambda expression to a member directly, for example, c = x =>{ x + 1 ;}; // 2. Do not declare the member name. The Member is from another object var ANN2 = new {ann1.a, ann1. B }; string STR = ann2.a; ann2.a = "str2"; // It is not allowed to assign values to anonymous type members in C #. Therefore, this line of code will cause an error during compilation: Object TMP = ann2. B; TMP = "str2"; // However, assign the reference type in the anonymous method to another variable and assign the value to the variable, the allowed int T = ann1.c (1) is used to change the value of an anonymous member );

　　

Ii. Anonymous type in VB

The anonymous type in VB is more flexible than that in C. Anonymous object members can be defined as read-only or writable, and anonymous methods are supported. Let's take a look at the example below.

'Define writable anonymous type dim ann1 = new {. A = "",. B = new object (),. C = function (byref X) as integer return x + 9 end function} 'Use the key keyword to define read-only anonymous members. In the following definition, member A is read-only, B is writable dim ANN2 = new with {key. A = "", ann1. B} ann1.a = "str" 'the anonymous type defined without the key keyword is writable ann2.a = "str"' the anonymous type defined with the key keyword is read-only, the error dim TMP as integer = ann1.c (1) is prompted during compilation)

Of course, the key keyword is not used to limit the read-only members, but to generate a hash value for an anonymous instance to compare whether two anonymous objects are the same object.

For example:

        Dim ann3 = New With {Key .A = "a",                           .B = "e"                           }        Dim ann4 = New With {Key .A = "a",                             .B = "3"                            }        If (ann3.Equals(ann4)) Then            ‘ ToDo........        End If

The above ann3 and ann4 are equal, because they are instances of the same anonymous type (so-called instances of the same anonymous type, only two members of the same anonymous type have the same name and member type ), and the key property has equal values.

C # differences between the anonymous type and the VB anonymous type