以泛型类型输入作为参数的 Lambda 表达式

Question

I want to make a method accept Expression like this

public class MyClass
{
  public void MyMethod( Expression<Func<T> expression)
  {}
}

public class FooClass
{
  public string Foo { get; set; }
}

MyClass A = new MyClass();

A.MyMethod( (FooClass x) => x.Foo );

How can I implement this? thank you in advance.

Answer 1

First of all, what is your goal in implementing such a class? What result do you want to return? Here is an example of how to use it for you

public class MyClass
{
  IQueryable<FooClass> myQuery;
  public MyClass()
  {
     myQuery = new List<FooClass>() { new FooClass() { Foo = "foo1"}, new FooClass() { Foo = "foo1" }, new FooClass() { Foo = "foo2" } }.AsQueryable();
  }
  public IQueryable<FooClass> WhereMethod(Expression<Func<FooClass, bool>> predicate)
  {
    try
    {
      return myQuery.Where(predicate);
    }
    catch
    {
      return null;
    }
  }
  public IQueryable<TResult> SelectMethod<TResult>(Expression<Func<FooClass, TResult>> predicate)
  {
     try
     {
       return myQuery.Select(predicate);
     }
     catch
     {
        return null;
     }
  }
}
public class FooClass
{
   public string Foo { get; set; }
}

now use

MyClass myClass = new MyClass();
var fooList = myClass.WhereMethod(a => a.Foo == "foo1").ToList();