生成代码-是否有一种简单的方法来获取可为null的类型的正确字符串表示形式？ [英] Generating code -- is there an easy way to get a proper string representation of nullable type?

问题描述

因此，我正在构建一个应用程序，该应用程序将使用C＃和VB输出（取决于项目设置）来生成大量代码。

So I'm building an application that is going to do a ton of code generation with both C# and VB output (depending on project settings).

我们有一个CodeTemplateEngine，它带有两个派生类VBTemplateEngine和CSharpTemplateEngine。这个问题涉及基于数据库表中的列创建属性签名。使用IDataReader的GetSchemaTable方法，我收集了列的CLR类型，例如 System.Int32，以及它是否为IsNullable。但是，我想使代码保持简单，而不要使用看起来像这样的属性：

I've got a CodeTemplateEngine, with two derived classes VBTemplateEngine and CSharpTemplateEngine. This question regards creating the property signatures based on columns in a database table. Using the IDataReader's GetSchemaTable method I gather the CLR type of the column, such as "System.Int32", and whether it IsNullable. However, I'd like to keep the code simple, and instead of having a property that looks like:

    public System.Int32? SomeIntegerColumn { get; set; }

或

    public Nullable<System.Int32> SomeIntegerColumn { get; set; },

使用此函数（从我的VBTemplateEngine）解析属性类型的地方，

where the property type would be resolved with this function (from my VBTemplateEngine),

    public override string ResolveCLRType(bool? isNullable, string runtimeType)
    {
        Type type = TypeUtils.ResolveType(runtimeType);
        if (isNullable.HasValue && isNullable.Value == true && type.IsValueType)
        {
            return "System.Nullable(Of " + type.FullName + ")";
            // or, for example...
            return type.FullName + "?";
        }
        else
        {
            return type.FullName;
        }
    },

我想生成一个更简单的属性。我讨厌从零开始构建Type字符串的想法，而宁愿有类似这样的东西：

I would like to generate a simpler property. I hate the idea of building a Type string from nothing, and I would rather have something like:

    public int? SomeIntegerColumn { get; set; }

任何地方都有内置的东西，例如在VBCodeProvider或CSharpCodeProvider类中会以某种方式使用

Is there anything built-in anywhere, such as in the VBCodeProvider or CSharpCodeProvider classes that would somehow take care of this for me?

还是有办法从类型中获取 int的类型别名？像 System.Nullable'1 [System.Int32] 这样的字符串？

Or is there a way to get a type alias of int? from a type string like System.Nullable'1[System.Int32]?

谢谢！

更新：

找到了可以做到的，但是我仍然对Type全名与其别名的映射类型保持警惕。

Found something that would do, but I'm still wary of that type of mapping of Type full names to their aliases.

推荐答案

您可以使用CodeDom对泛型类型的支持和GetTypeOutput方法来做到这一点：

You can do this using CodeDom's support for generic types and the GetTypeOutput method:

CodeTypeReference ctr;
if (/* you want to output this as nullable */)
{
  ctr = new CodeTypeReference(typeof(Nullable<>));
  ctr.TypeArguments.Add(new CodeTypeReference(typeName));
}
else
{
  ctr = new CodeTypeReference(typeName);
}
string typeName = codeDomProvider.GetTypeOutput(ctr);

这将尊重特定于语言的类型关键字，例如C＃ int 或VB Integer ，尽管它仍会为您提供 System.Nullable< int> 而不是 int？。

This will respect language-specific type keywords such as C# int or VB Integer, though it will still give you System.Nullable<int> rather than int?.

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