打印出Linq表达式树层次结构 [英] Print out Linq Expression Tree Hierarchy
问题描述
动态语言运行库(DLR)具有一些非常酷的代码用于Expression,包括一些非常好的代码以打印出我想使用的Expression树,以便:
The dynamic language runtime (DLR) has some pretty cool code for Expression's, including some very nice code to print out Expression trees which I want to use so that:
int a = 1;
int b = 2;
Expression<Func<int, int>> expression = (c) => a + (b * c)
expression.Evaluate(5, stringBuilder)
输出:
(5) => a + (b * c) = 11 Where
a = 1
b * c = 10 Where
b = 2
c = 5
我在网上发现了一些代码可以做到这一点,但发现只有在表达式不包含任何参数的情况下,它才有效.
I found some code on the net to do this but found that it only works if the expressiontakes in no arguments.
然后,我发现了类似方法的DLR实现.但是DLR具有自己的Expression类和许多其他标准C#类型的自定义实现,因此我有些困惑.有人知道我该如何实现吗?
I then discovered the DLR implementation of a similar method. However the DLR has its own custom implementations of the Expression class and many other standard C# types so I got a little confused. Anyone know how I can implement the above?
推荐答案
怎么样:
using System;
using System.Linq;
using System.Linq.Expressions;
using System.Text;
using System.Text.RegularExpressions;
static class Program
{
static void Main()
{
int a = 1, b = 2;
StringBuilder sb = new StringBuilder();
Expression<Func<int, int>> expression = (c) => a + (b * c);
expression.Evaluate(sb, 5);
// now fix the capture class names (from a and b)
string s = sb.ToString();
s = Regex.Replace(s, @"value\([^)]+\)\.", "");
Console.WriteLine(s);
}
public static void Evaluate(this LambdaExpression expr, StringBuilder builder, params object[] args)
{
var parameters = expr.Parameters.ToArray();
if (args == null || parameters.Length != args.Length) throw new ArgumentException("args");
Evaluate(expr.Body, 0, builder, parameters, args);
}
private static StringBuilder Indent(this StringBuilder builder, int depth)
{
for (int i = 0; i < depth; i++) builder.Append(" ");
return builder;
}
private static void Evaluate(this Expression expr, int depth, StringBuilder builder, ParameterExpression[] parameters, object[] args)
{
builder.Indent(depth).Append(expr).Append(" = ").Append(Expression.Lambda(expr, parameters).Compile().DynamicInvoke(args));
UnaryExpression ue;
BinaryExpression be;
ConditionalExpression ce;
if ((ue = expr as UnaryExpression) != null)
{
builder.AppendLine(" where");
Evaluate(ue.Operand, depth + 1, builder, parameters, args);
}
if ((be = expr as BinaryExpression) != null)
{
builder.AppendLine(" where");
Evaluate(be.Left, depth + 1, builder, parameters, args);
Evaluate(be.Right, depth + 1, builder, parameters, args);
}
else if ((ce = expr as ConditionalExpression) != null)
{
builder.AppendLine(" where");
Evaluate(ce.Test, depth + 1, builder, parameters, args);
Evaluate(ce.IfTrue, depth + 1, builder, parameters, args);
Evaluate(ce.IfFalse, depth + 1, builder, parameters, args);
}
else
{
builder.AppendLine();
}
}
}
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