Reflector生成Lambda表达式，如何取回实际的Linq查询？

Question

我正在使用 Reflector 反编译一些二进制文件。我在使用 Lambda 表达式和 方法 时遇到问题编译。 lambda 表达式对我来说似乎非常复杂，我不知道如何将其转换回可编译的 LINQ 代码。这是代码：

public double? LoadSumRialAmount(long functionId, long? subFunctionId)
{
        ParameterExpression expression;
        if (!subFunctionId.HasValue)
        {
            return (from func in base.MetaData.SubFunction
                where func.FunctionId == functionId
                select func).Select<SubFunctionEntity, double?>(System.Linq.Expressions.Expression.Lambda<Func<SubFunctionEntity, double?>>(System.Linq.Expressions.Expression.Multiply(System.Linq.Expressions.Expression.Property(expression = System.Linq.Expressions.Expression.Parameter(typeof(SubFunctionEntity), "func"), (MethodInfo) methodof(SubFunctionEntity.get_Volume)), System.Linq.Expressions.Expression.Property(expression, (MethodInfo) methodof(SubFunctionEntity.get_RialAmount))), new ParameterExpression[] { expression })).Sum();
        }
        return (from func in base.MetaData.SubFunction
            where (func.FunctionId == functionId) && (func.SubFunctionId != subFunctionId)
            select func).Select<SubFunctionEntity, double?>(System.Linq.Expressions.Expression.Lambda<Func<SubFunctionEntity, double?>>(System.Linq.Expressions.Expression.Multiply(System.Linq.Expressions.Expression.Property(expression = System.Linq.Expressions.Expression.Parameter(typeof(SubFunctionEntity), "func"), (MethodInfo) methodof(SubFunctionEntity.get_Volume)), System.Linq.Expressions.Expression.Property(expression, (MethodInfo) methodof(SubFunctionEntity.get_RialAmount))), new ParameterExpression[] { expression })).Sum();
}

ps 另一个错误是 SubFunctionEntity 类具有“Volume”属性，我不明白为什么此代码在其上调用某种静态属性，例如： SubFunctionEntity.get_Volume

Answer 1

您是否尝试过ILSpy？它甚至有一些选项来控制您是否想要生成 LINQ“函数”语法或 from...where 语法（View->Options->Decompiler->Decompile query expression 和 反编译匿名方法/lambdas）

对于您的其他问题：SubFunctionEntity.get_Volume 是类的属性 Volume 的 getter 子函数实体。

(MethodInfo) methodof(SubFunctionEntity.get_Volume) 与 typeof(SubFunctionEntity).GetProperty("Volume").GetGetMethod() 相同，仅在编译时完成，而不是在运行时。问题是 C# 没有“函数”方法。

如果您确实想使用 Reflector 提供的内容，这是“更正”版本：

public double? LoadSumRialAmount(long functionId, long? subFunctionId)
{
    ParameterExpression expression;
    if (!subFunctionId.HasValue)
    {
        return (from func in base.MetaData.SubFunction
                where func.FunctionId == functionId
                select func).Select<SubFunctionEntity, double?>(Expression.Lambda<Func<SubFunctionEntity, double?>>(Expression.Multiply(Expression.Property(expression = Expression.Parameter(typeof(SubFunctionEntity), "func"), typeof(SubFunctionEntity).GetProperty("Volume").GetGetMethod()), Expression.Property(expression, typeof(SubFunctionEntity).GetProperty("RialAmount").GetGetMethod())), new ParameterExpression[] { expression })).Sum();
    }
    return (from func in base.MetaData.SubFunction
            where (func.FunctionId == functionId) && (func.SubFunctionId != subFunctionId)
            select func).Select<SubFunctionEntity, double?>(Expression.Lambda<Func<SubFunctionEntity, double?>>(Expression.Multiply(Expression.Property(expression = Expression.Parameter(typeof(SubFunctionEntity), "func"), typeof(SubFunctionEntity).GetProperty("Volume").GetGetMethod()), Expression.Property(expression, typeof(SubFunctionEntity).GetProperty("RialAmount").GetGetMethod())), new ParameterExpression[] { expression })).Sum();
}

请注意，您需要一些使用：

using System.Linq;
using System.Linq.Expressions;

啊...最复杂的表达式是： func =>; (func.Volume * func.RialAmount) 因此您可以将该方法编写为：

public double? LoadSumRialAmount(long functionId, long? subFunctionId)
{
    if (!subFunctionId.HasValue)
    {
        return (from func in base.MetaData.SubFunction
                where func.FunctionId == functionId
                select func).Select(func => (func.Volume * func.RialAmount)).Sum();
    }
    return (from func in base.MetaData.SubFunction
            where (func.FunctionId == functionId) && (func.SubFunctionId != subFunctionId)
            select func).Select(func => (func.Volume * func.RialAmount)).Sum();
}

附录：检查后，ILSpy 会产生与 Reflector 类似但不同的随机垃圾