将包含转换为表达式树 [英] Convert Contains To Expression Tree

问题描述

与以下内容相关:创建具有3个条件的Lambda表达式

请考虑以下代码:

from a in myTbl
where a.Address.Contains(strToCheck)
select a

如何将其转换为表达式树并使用表达式编写以上代码? 主要问题是将a.Address.Contains(strToCheck)转换为Expression Tree.

How I can convert this to Expression Tree and write above code with Expressions? Main Problem is converting a.Address.Contains(strToCheck) to Expression Tree.

编辑1)地址是 string 字段，而strToCheck是 string

Edit 1) Address is a string field and strToCheck is a string

谢谢

推荐答案

a.Address.Contains(strToCheck)表示对

a.Address.Contains(strToCheck) represents a call to string.Contains instance method on a.Address instance with strToCheck argument.

构建相应表达式的最简单方法是使用以下 Expression.Call重载:

The simplest way to build the corresponding expression is to use the following Expression.Call overload:

public static MethodCallExpression Call(
    Expression instance,
    string methodName,
    Type[] typeArguments,
    params Expression[] arguments
)

像这样(使用链接的问题中的术语):

like this (using the terms from the linked question):

var body = Expression.Call(
    Expression.PropertyOrField(param, "Address"), // instance
    "Contains", // method
    Type.EmptyTypes, // no generic type arguments
    Expression.Constant(strToCheck) // argument
);

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