使用反射从属性名称获取 lambda 表达式 [英] Use reflection to get lambda expression from property Name

问题描述

我想让用户可以选择按不同的属性进行搜索.例如

I want to give the user the choice of searching by different properties. For instance

[输入文本] |[选择选项{ID、姓名、电话}] |[搜索]

[INPUT TEXT] | [SELECT OPTION {ID, NAME, PHONE}] | [SEARCH]

我稍后会像这样构建我的查询:

And I would later build my query like this:

repository.Where(lambda-expression)

从所选选项 {ID, NAME, PHONE} 构建 lambda 表达式的地方(例如:x => x.NAME.Equals(INPUT TEXT))

Where lambda-expression is build from the selected option {ID, NAME, PHONE} (For example: x => x.NAME.Equals(INPUT TEXT))

是否可以使用反射从属性名称构建 lambda?

Is there a way to build the lambda from the Property name perhaps using reflection?

谢谢

推荐答案

您无需构建 lambda 表达式 - 您构建的是表达式树.这并不难，但需要一点耐心.在您的示例中，您可能需要:

You don't build a lambda expression - you build an expression tree. It's not terribly hard, but it takes a little patience. In your sample you'd probably need:

ParameterExpression parameter = Expression.Parameter(typeof(Foo), "x");
Expression property = Expression.Property(parameter, propertyName);
Expression target = Expression.Constant(inputText);
Expression equalsMethod = Expression.Call(property, "Equals", null, target);
Expression<Func<Foo, bool>> lambda =
   Expression.Lambda<Func<Foo, bool>>(equalsMethod, parameter); 

假设:

• 存储库元素类型为 Foo
• 您想使用名为 propertyName
的属性
• 您想与 inputText
比较是否相等

• The repository element type is Foo
• You want to use a property called propertyName
• You want to compare for equality against inputText

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