create Expression method with reflection in c#

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This is what I want to make:

C#

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

d is a Model. my model name is JN_News

I start to write code :

C#

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);

Posted 26-Aug-14 1:06am

Mojtaba Dinarvand

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vikinghunter 27-Aug-14 2:15am

Let me have a try..

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This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

vikinghunter · Answer 1 · 2014-08-26T20:13:00

Is this you want?

C#

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);

In my imagination,your models should look like this:

C#

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

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

create Expression method with reflection in c#

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create Expression method with reflection in c#

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