用對象初始化器創建實例的表達式

Question

有沒有什麼方法可以用對象初始值設定器和表達式樹來創建對象的實例？我的意思是創建一個表達式樹構建這個拉姆達：

// my class 
public class MyObject { 
    public bool DisplayValue { get; set; } 
} 

// my lambda: 
var lambda = (Func<bool, MyObject>) 
      (displayValue => new MyObject { DisplayValue = displayValue }); 

如何創建這個拉姆達與表達式樹？

UPDATE：

我tryed自己寫下面的代碼：

public static Func<bool, dynamic> Creator; 

    static void BuildLambda() { 
     var expectedType = typeof(MyObject); 
     var displayValueParam = Expression.Parameter(typeof(bool), "displayValue"); 
     var ctor = Expression.New(expectedType); 
     var local = Expression.Parameter(expectedType, "obj"); 
     var displayValueProperty = Expression.Property(ctor, "DisplayValue"); 

     var returnTarget = Expression.Label(expectedType); 
     var returnExpression = Expression.Return(returnTarget,local, expectedType); 
     var returnLabel = Expression.Label(returnTarget, Expression.Default(expectedType)); 

     var block = Expression.Block(
      new[] { local }, 
      Expression.Assign(local, ctor), 
      Expression.Assign(displayValueProperty, displayValueParam), 
      Expression.Return(Expression.Label(expectedType), local, expectedType), 
      returnExpression, 
      returnLabel 
      ); 
     Creator = 
      Expression.Lambda<Func<bool, dynamic>>(block, displayValueParam) 
       .Compile(); 
    } 

但它引發以下錯誤：

Cannot jump to undefined label ''.

大家可以幫我嗎？

Answer 1

，代表了一個表達的對象初始化，您應該使用Expression.MemberInit()：

Expression<Func<bool, MyObject>> BuildLambda() { 
    var createdType = typeof(MyObject); 
    var displayValueParam = Expression.Parameter(typeof(bool), "displayValue"); 
    var ctor = Expression.New(createdType); 
    var displayValueProperty = createdType.GetProperty("DisplayValue"); 
    var displayValueAssignment = Expression.Bind(
     displayValueProperty, displayValueParam); 
    var memberInit = Expression.MemberInit(ctor, displayValueAssignment); 

    return 
     Expression.Lambda<Func<bool, MyObject>>(memberInit, displayValueParam); 
} 

爲了驗證這一點其實你想要做什麼，你可以在創建表達致電ToString()。在這種情況下，如預期的輸出：

displayValue => new MyObject() {DisplayValue = displayValue} 

Answer 2

終於讓我找到我的答案：

public static Func<bool, dynamic> Creator; 

static void BuildLambda() { 
    var expectedType = typeof(MyObject); 
    var displayValueParam = Expression.Parameter(typeof(bool), "displayValue"); 
    var ctor = Expression.New(expectedType); 
    var local = Expression.Parameter(expectedType, "obj"); 
    var displayValueProperty = Expression.Property(local, "DisplayValue"); 

    var returnTarget = Expression.Label(expectedType); 
    var returnExpression = Expression.Return(returnTarget,local, expectedType); 
    var returnLabel = Expression.Label(returnTarget, Expression.Default(expectedType)); 

    var block = Expression.Block( 
     new[] { local }, 
     Expression.Assign(local, ctor), 
     Expression.Assign(displayValueProperty, displayValueParam), 
     /* I forgot to remove this line: 
     * Expression.Return(Expression.Label(expectedType), local, expectedType), 
     * and now it works. 
     * */ 
     returnExpression, 
     returnLabel 
     ); 
    Creator = 
     Expression.Lambda<Func<bool, dynamic>>(block, displayValueParam) 
      .Compile(); 
} 

UPDATE：

雖然它工作正常，但@svick提供他的回答更好和更短的方式，是actuallt wath我一直在尋找：MemberInit。請參閱@ svick的答案。