Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
605 views
in Technique[技术] by (71.8m points)

c# - Incorrect number of parameters supplied for lambda declaration

Please have a look at my code: I'm trying to create myCar with an Expression Tree.

I get an ArgumentException on this line var m = Expression.Lambda<Func<Engine,... The message is Incorrect number of parameters supplied for lambda declaration.

public class Engine
{
    public string Name { get; private set; }
    public Engine(string name)
    {
        Name = name;
    }
}
public class Car
{
    private readonly Engine engine;
    public Car(Engine engine)
    {
        this.engine = engine;
    }
    public string GetEngineName(){return engine.Name;}
}
class Program
{
    static void Main(string[] args)
    {
        var ci = typeof (Car).GetConstructor(new[] {typeof (Engine)});

        var engine = Expression.Parameter(typeof (Engine));

        var m = Expression.Lambda<Func<Engine,Car>>(Expression.New(ci, engine))
                          .Compile();

        var myCar = m(new Engine("TDI 2.0"));
        var s = myCar.GetEngineName();
    }
}

I can't figure out what's wrong and where I did the error. Thanks in advance.

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

You must specify the engine in the 'params ParameterExpression[] parameters' part of Expression.Lambda

var m = Expression.Lambda<Func<Engine, Car>>(Expression.New(ci, engine), engine)

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...