C# 表达式树Expression

表达式相加

//常量表达式
Expression firstArg = Expression.Constant(2);
Expression secondArg = Expression.Constant(4);

//相加
Expression addExpression = Expression.Add(firstArg, secondArg);
Console.WriteLine(addExpression.ToString());

将表达式编译成委托

Console.WriteLine("将表达式编译成委托");
Expression<Func<int>> expression = Expression.Lambda<Func<int>>(addExpression);
Console.WriteLine(expression);

var func = expression.Compile();
Console.WriteLine(func);
Console.WriteLine("结果：" + func());

将Lamda表达式转换成表达式

Expression<Func<int>> expression = () => 5;

Console.WriteLine(expression);
Console.WriteLine(expression.Compile());
Console.WriteLine(expression.Compile()());

获得表达式信息

Expression<Func<int, int, double, double>> expression = (num1, num2, num3) => (num1 + 5) * num2 / num3;
Console.WriteLine(expression.ToString());
Console.WriteLine(expression.Compile());
Console.WriteLine(expression.Compile()(1, 2, 3));

if (expression.NodeType == ExpressionType.Lambda)
{
    //LambdaExpression继承于Expression
    var lambdaExpression = expression as LambdaExpression;
    Console.WriteLine(lambdaExpression.Body);
    Console.WriteLine("返回值类型：" + lambdaExpression.ReturnType.ToString());

    IReadOnlyList<ParameterExpression> parameters = lambdaExpression.Parameters;

    foreach (var parameter in parameters)
    {
        Console.WriteLine("形参名： " + parameter.Name);
        Console.WriteLine("形参类型： " + parameter.Type.Name);
    }
}

拆分左右节点

Console.WriteLine("表达式详细信息");
Console.WriteLine();

//基本信息
Expression<Func<int, int, int>> sumExpression = (num1, num2) => num1 + (5 + num2);
Console.WriteLine($"根节点的节点类型：{sumExpression.NodeType}");
Console.WriteLine($"根节点的类型：{sumExpression.Type.Name}");
Console.WriteLine($"根节点的名字：{sumExpression.Name}");
Console.WriteLine($"根节点的代码：{sumExpression.ToString()}");
Console.WriteLine();

//形参
Console.WriteLine($@"表达式的形参：{sumExpression.Parameters.Count}个,");
foreach (var item in sumExpression.Parameters)
{
    Console.WriteLine($"节点的节点类型：{sumExpression.Parameters[0].NodeType},");
    Console.WriteLine($"类型：{sumExpression.Parameters[0].Type.Name},");
    Console.WriteLine($"参数的名字：{sumExpression.Parameters[0]}");
}
Console.WriteLine();

//Body
var sumBody = sumExpression.Body as BinaryExpression;

Console.WriteLine($"主体节点的节点类型：{sumBody.NodeType}");
Console.WriteLine($"主体节点代码：{sumBody.ToString()}");
Console.WriteLine();

//左节点
var leftNode = sumBody.Left as ParameterExpression;
Console.WriteLine($"主体左节点：{leftNode.ToString()}");
Console.WriteLine($"主体左节点的节点类型：{leftNode.NodeType}");
Console.WriteLine($"主体左节点的类型：{leftNode.Type.Name}");
Console.WriteLine($"主体左节点的名字：{leftNode.Name}");
Console.WriteLine();

//右节点
var rightNode = sumBody.Right as BinaryExpression;
Console.WriteLine($"主体右节点：{rightNode.ToString()}");
Console.WriteLine($"主体右节点的节点类型：{rightNode.NodeType}");
Console.WriteLine($"主体右节点的类型：{rightNode.Type.Name}");
Console.WriteLine();

//继续拆分右节点
//(5 + num2)
//右节点的左节点
var rightLeftNode = rightNode.Left as ConstantExpression;
Console.WriteLine($"右节点的左节点：{rightLeftNode.ToString()}");
Console.WriteLine($"右节点的左节点的节点类型：{rightLeftNode.NodeType}");
Console.WriteLine($"右节点的左节点的类型：{rightLeftNode.Type.Name}");
Console.WriteLine();

//右节点的右节点
var rightRightNode = rightNode.Right as ParameterExpression;
Console.WriteLine($"右节点的右节点：{rightRightNode.ToString()}");
Console.WriteLine($"右节点的右节点的节点类型：{rightRightNode.NodeType}");
Console.WriteLine($"右节点的右节点的类型：{rightRightNode.Type.Name}");
Console.WriteLine($"右节点的右节点的名字：{rightRightNode.Name}");

示例代码

ExpressionTestDemo

参考资料

表达式树 (C#)
Expression.NodeType 属性