用c＃中的反射创建表达式方法 [英] create Expression method with reflection in c#

问题描述

这就是我想要的：

This is what I want to make:

output.Where(d => d.JN_NewsCategories.NewsCategoriesEn.Contains("event"));

d是模型。我的型号名称是JN_News



我开始编写代码：

d is a Model. my model name is JN_News

I start to write code :

var modelName = "JN_News";
var subModelName = "JN_NewsCategories";
var subModelField = "NewsCategoriesEn";
var splitSeacrh="event";

Type modelClass = GetModel(modelName);
ParameterExpression peSubModel = Expression.Parameter(modelClass, "x");
//Note this line:
Expression left= Expression.Property(peSubModel, modelClass.GetProperty(subModelName));
// left= x.JN_NewsCategories
//How do I access the field.  Like this : x.JN_NewsCategories.NewsCategoriesEn
// I tried very hard but did not succeed
Expression right= Expression.Constant(splitSeacrh);
MethodCallExpression conditionExpressionSubModel = Expression.Call(left,
typeof(string).GetMethod("Contains"), right);

推荐答案

这是你想要的吗？

Is this you want?

var modelName = "JN_News";
var subModelName = "JN_NewsCategories";
var subModelField = "NewsCategoriesEn";
var splitSeacrh = "event";

Type modelClass = GetModel(modelName);
ParameterExpression peSubModel = Expression.Parameter(modelClass, "x");

Expression left = Expression.Property(peSubModel, modelClass.GetProperty(subModelName));

left = Expression.Field(left, modelClass.GetProperty(subModelName).PropertyType.GetField(subModelField));

Expression right = Expression.Constant(splitSeacrh, typeof(string));

MethodCallExpression conditionExpressionSubModel = Expression.Call(left,

typeof(string).GetMethod("Contains", new Type[] { typeof(string) }), right);

在我的想象中，你的模型应如下所示：

In my imagination,your models should look like this:

class JN_News
{
    public Categories JN_NewsCategories { get; set; }
}

class Categories
{
    public string NewsCategoriesEn = "eventForSomething";
}

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