动态 Linq - 在运行时设置 orderby 表达式类型

发布于 2024-07-23 09:58:26 字数 1271 浏览 3 评论 0原文

我正在使用动态 Linq 并让 where 子句发挥作用。现在我想添加 orderby 子句，但在设置动态表达式的类型时遇到问题。下面是我的工作代码：

class MyClass {
    public string Owner;
    public DateTime Inserted;
}

Expression<Func<MyClass, bool>> whereExpression = DynamicExpression.ParseLambda<MyClass, bool>("owner = \"joe\"");
Expression<Func<MyClass, DateTime>> orderExpression = DynamicExpression.ParseLambda<MyClass, DateTime>("inserted");
var result = from item in table.Where(whereExpression).OrderBy(orderExpression) select item;
result.ToList().ForEach(m => Console.WriteLine("inserted=" + m.Inserted + "."));

因为我需要在 orderby 表达式中使用不同的属性，所以我希望能够使用类似于下面的代码之类的代码，但该代码不起作用。

Expression<Func<MyClass, bool>> whereExpression = DynamicExpression.ParseLambda<MyClass, bool>("owner = \"joe\"");
Type orderType = typeof(DateTime);
Expression<Func<MyClass, orderType>> orderExpression = DynamicExpression.ParseLambda<MyClass, orderType>("inserted");
var result = from item in table.Where(whereExpression).OrderBy(orderExpression) select item;
result.ToList().ForEach(m => Console.WriteLine("inserted=" + m.Inserted + "."));

编译器对声明 orderExpression 的行不满意。有没有办法在运行时设置 Func 的类型？

原文

I'm using dynamic Linq and have the where clauses working. Now I'm looking to add orderby clauses but am having a problem being able to set the type of the dynamic expression. Below is working code that I have:

class MyClass {
    public string Owner;
    public DateTime Inserted;
}

Expression<Func<MyClass, bool>> whereExpression = DynamicExpression.ParseLambda<MyClass, bool>("owner = \"joe\"");
Expression<Func<MyClass, DateTime>> orderExpression = DynamicExpression.ParseLambda<MyClass, DateTime>("inserted");
var result = from item in table.Where(whereExpression).OrderBy(orderExpression) select item;
result.ToList().ForEach(m => Console.WriteLine("inserted=" + m.Inserted + "."));

Because I need to use different properties in the orderby expression what I'd like to be able to do is use something like the code below which is not working.

Expression<Func<MyClass, bool>> whereExpression = DynamicExpression.ParseLambda<MyClass, bool>("owner = \"joe\"");
Type orderType = typeof(DateTime);
Expression<Func<MyClass, orderType>> orderExpression = DynamicExpression.ParseLambda<MyClass, orderType>("inserted");
var result = from item in table.Where(whereExpression).OrderBy(orderExpression) select item;
result.ToList().ForEach(m => Console.WriteLine("inserted=" + m.Inserted + "."));

The compiler isn't happy with the line delcaring the orderExpression. Is there any way to set the type of a Func at runtime?

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瑾兮 2024-07-30 09:58:26

看起来动态 Linq 扩展方法为我处理了这一切。我太难了。

var result = from item in table.Where("owner = \"joe\"").OrderBy("inserted") select item;
result.ToList().ForEach(m => Console.WriteLine("inserted=" + m.Inserted + "."));

Looks like the dynamic Linq extension methods take care of it all for me. I was making it too hard.

var result = from item in table.Where("owner = \"joe\"").OrderBy("inserted") select item;
result.ToList().ForEach(m => Console.WriteLine("inserted=" + m.Inserted + "."));

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