在 C# 3.0 中，我们使用“var” C# 2.0 中的替代方案是什么？

发布于 2024-07-20 04:25:42 字数 661 浏览 7 评论 0原文

我正在使用托管扩展框架（MEF）学习 .Net 中的可插入架构。我在网上看到了示例代码，但是当我尝试实现它时，我陷入了困境。

代码使用：

 var catalog = new AttributedAssemblyPartCatalog(Assembly.GetExecutingAssembly());
 var container = new CompositionContainer(catalog.CreateResolver());

This var is available on C# 3.0，而我正在 C# 2.0 中编码。

上述两种说法的替代方案是什么？如何使用 VS 2005 让它们在 c# 2.0 中工作？

我尝试了这个 bt 它现在说

错误 1 无法找到类型或命名空间名称“AttributedAssemblyPartCatalog”（您是否缺少 using 指令或程序集引用？） C:\Documents and Settings\test\ Desktop\MEFDemo\MEFDemo\Program.cs 31 13 MEFDemo

其中我添加了对 SystemComponentModel.Composition 的引用

原文

I am learning plug able architecture in .Net using Managed Extensibility Framework (MEF.)
I saw sample code on the net, but when I tried to implement it I got stuck at one point.

The code was using:

 var catalog = new AttributedAssemblyPartCatalog(Assembly.GetExecutingAssembly());
 var container = new CompositionContainer(catalog.CreateResolver());

This var is available on C# 3.0 where as I am coding in C# 2.0.

What is the alternative of above two statements? How can I make them work in c# 2.0 using VS 2005?

i tried this bt its saying now

Error 1 The type or namespace name 'AttributedAssemblyPartCatalog' could not be found (are you missing a using directive or an assembly reference?) C:\Documents and Settings\test\Desktop\MEFDemo\MEFDemo\Program.cs 31 13 MEFDemo

where as i have added referance to SystemComponentModel.Composition

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|煩躁 2024-07-27 04:25:42

基本上，var 强制编译器根据变量的“初始化程序”来确定（推断）变量的编译时类型 - 实际上是 < 右侧的表达式代码>=符号。这里的类型很明显：

AttributedAssemblyPartCatalog catalog = 
    new AttributedAssemblyPartCatalog(Assembly.GetExecutingAssembly());
CompositionContainer container = 
    new CompositionContainer(catalog.CreateResolver());

并确保添加 using System.ComponentModel.Composition; 语句。另外，请注意，AttributedAssemblyPartCatalog 已重命名为 AssemblyCatalog。

Basically, var forces the compiler to determine (infer) the compile-time type of a variable based on it's "initializer" -- effectively, an expression to the right from = sign. Here the types are obvious:

AttributedAssemblyPartCatalog catalog = 
    new AttributedAssemblyPartCatalog(Assembly.GetExecutingAssembly());
CompositionContainer container = 
    new CompositionContainer(catalog.CreateResolver());

And make sure you add using System.ComponentModel.Composition; statement. Plus, be advised that AttributedAssemblyPartCatalog was renamed to AssemblyCatalog.

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始终不够 2024-07-27 04:25:42

这就是C# 3.0中类型推断的使用。

在 c# 3.0 中使用关键字时，

var

编译器会推断类型。请参阅 scott Guthries 解释

在 c# 2.0 中，您必须声明与 c# 1.1 相同的变量类型，

例如

Type variableName = new Type();

让你上面的代码示例

AttributedAssemblyPartCatalog catalog = new AttributedAssemblyPartCatalog(Assembly.GetExecutingAssembly());

CompositionContainer container = new CompositionContainer(catalog.CreateResolver());

HTH

This is the use of type inference in C# 3.0.

When using the keyword

var

in c# 3.0 the compiler infers the type. See scott guthries explanation

In c# 2.0 you have to declare the type of the variable the same as c# 1.1

e.g.

Type variableName = new Type();

Making you above code example

AttributedAssemblyPartCatalog catalog = new AttributedAssemblyPartCatalog(Assembly.GetExecutingAssembly());

CompositionContainer container = new CompositionContainer(catalog.CreateResolver());

HTH

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羁〃客ぐ 2024-07-27 04:25:42

AttributedAssemblyPartCatalog catalog = new 
    AttributedAssemblyPartCatalog(Assembly.GetExecutingAssembly());

CompositionContainer container = new 
    CompositionContainer(catalog.CreateResolver());

AttributedAssemblyPartCatalog catalog = new 
    AttributedAssemblyPartCatalog(Assembly.GetExecutingAssembly());

CompositionContainer container = new 
    CompositionContainer(catalog.CreateResolver());

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橘亓 2024-07-27 04:25:42

C# 中的变量仍然是强类型的。 var 是隐式类型 - 请参阅 MSDN。

在大多数情况下，这仅意味着您必须减少输入，但在某些情况下这是必要的 - 在我链接到的页面上的第二个示例中：

必须使用
var 因为结果
是匿名类型的集合，
并且该类型的名称不是
除编译器外均可访问
本身。

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宫墨修音 2024-07-27 04:25:42

var 是一个 C# 3.0 关键字，除了从初始化值推断强类型之外什么也不做。

如果没有 var，您可以手动执行编译器在幕后执行的操作；您在声明中指定变量的类型。

因此;

AttributedAssemblyPartCatalog catalog = new 
    AttributedAssemblyPartCatalog(Assembly.GetExecutingAssembly());

CompositionContainer container = new 
    CompositionContainer(catalog.CreateResolver());

var is a C# 3.0 keyword and does nothing other than inferring the strong type from the initialization value.

In the absence of var, you manually do what the compiler is doing behind the scenes; you specify the type of the variable in the declaration.

Hence;

AttributedAssemblyPartCatalog catalog = new 
    AttributedAssemblyPartCatalog(Assembly.GetExecutingAssembly());

CompositionContainer container = new 
    CompositionContainer(catalog.CreateResolver());

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