C＃，create（method？）表达式并调用它 [英] C#, create (method?) expression and call it

问题描述

我真的是c＃表达式的新手。我有一些类似的东西

  class SimpleClass 
 {
 private string ReturnString（string InputString）
 {
 returnresult is：+ InputString; 
} 
 
 public string返回（表达式exp）
 {
 LambdaExpression lambda = Expression.Lambda（exp）; 
 return lambda.Compile（）; 
} 
} 
  

现在，我想调用这个方法Return with一些paramter的东西（伪）这样：

  SimpleClass sc = new SimpleClass（）; 
表达式表达式= Expression.MethodCall（//如何使用一些参数创建表达式来调用SimpleClass.ReturnString）; 
 string result = sc.Return（expression）; 
 Console.WriteLine（result）; 
  

感谢您的帮助/回答。

Matt

解决方案

尽早执行 exp 签名尽可能 - 即作为表达式< Func< string>>

  public string Return（Expression< Func< string>> expression）
 {
 return expression.Compile（）（）; 
} 
  

与：

  SimpleClass sc = new SimpleClass（）; 
 string result = sc.Return（（）=> sc.ReturnString（hello world））; 
 Console.WriteLine（result）; 
  

或：

 code> SimpleClass sc = new SimpleClass（）; 
表达式表达式= Expression.Call（
 Expression.Constant（sc），// target-object 
ReturnString，// method-name 
 null，// generic type -argments 
 Expression.Constant（hello world）//方法参数
）; 
 var lambda = Expression.Lambda< Func< string>>（expression）; 
 string result = sc.Return（lambda）; 
 Console.WriteLine（result）; 
  

当然，委托使用（ Func< string> ）可能在许多情况下也可以正常工作。

I'm realtively new to c# expression. I have some class something like that

class SimpleClass
{
    private string ReturnString(string InputString)
    {
        return "result is: "+InputString;
    }

    public string Return(Expression exp)
    {
        LambdaExpression lambda = Expression.Lambda(exp);
        return lambda.Compile();
    }
}

Now, I would like to call this method Return with some paramter something (pseudo) like this:

      SimpleClass sc = new SimpleClass();
      Expression expression = Expression.MethodCall(//how to create expression to call SimpleClass.ReturnString with some parameter?);
     string result = sc.Return(expression);
    Console.WriteLine(result);

Thanks for help/answer.

Matt

解决方案

It would be better to enforce the exp signature as early as possible - i.e. as an Expression<Func<string>>

public string Return(Expression<Func<string>> expression)
{
    return expression.Compile()();
}

with either:

SimpleClass sc = new SimpleClass();
string result = sc.Return(() => sc.ReturnString("hello world"));
Console.WriteLine(result);

or:

SimpleClass sc = new SimpleClass();
Expression expression = Expression.Call(
    Expression.Constant(sc),           // target-object
    "ReturnString",                    // method-name
    null,                              // generic type-argments
    Expression.Constant("hello world") // method-arguments
);
var lambda = Expression.Lambda<Func<string>>(expression);
string result = sc.Return(lambda);
Console.WriteLine(result);

Of course, delegate usage (Func<string>) might work just as well in many scenarios.

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