Expression.Lambda 和在运行时生成查询，嵌套属性 “Where” 示例

Question

我在有关为 Where 查询构建表达式树的问题上找到了非常好的答案。

Expression.Lambda and query generation at runtime, simplest "Where" example

谁能帮我看看这个例子如何在嵌套属性的场景中实现。我的意思是：

var result = query.Where(item => item.Name == "Soap")

有了那个解决方案：

var item = Expression.Parameter(typeof(Item), "item");

var prop = Expression.Property(item, "Name");

var soap = Expression.Constant("Soap");

var equal = Expression.Equal(prop, soap);

var lambda = Expression.Lambda<Func<Item, bool>>(equal, item);

var result = queryableData.Where(lambda);

如何为以下内容构建树？

var result = query.Where(item => item.Data.Name == "Soap").

Answer 1

（此答案最初由问题中的 OP 发布。）

问题可以通过以下方式解决：

var item = Expression.Parameter(typeof(Item), "item");

var dataExpr = Expression.Property(item, "Data");

var prop = Expression.Property(dataExpr, "Name");

var soap = Expression.Constant("Soap");

var equal = Expression.Equal(prop, soap);

var lambda = Expression.Lambda<Func<Item, bool>>(equal, item);

var result = queryableData.Where(lambda);

Answer 2

这与上面发布的答案相同，但我发现它在可视化表达式树方面更具可读性：

var parameterItem = Expression.Parameter(typeof(Item), "item");

var lambda = Expression.Lambda<Func<Item, bool>>(
    Expression.Equal(
        Expression.Property(
            Expression.Property(
                parameterItem, 
                "Data"
            ), 
            "Name"
        ), 
        Expression.Constant("Soap")
    ), 
    parameterItem
);

var result = queryableData.Where(lambda);

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