Access property in lambda expression from string when using LINQ

Question

How can I do something like this:

var result = db.MyTable.Where(x => x."MyProperty" == "Test" );

As you can see I want to access "MyProperty" but give the property name as a sting.

Answer 1

You could use reflection

x.GetType( ).GetProperty("MyProperty").GetValue( x, null ); 

although this might work, i wouldn't advise on doing this, why don't pass in your where clause as an expression like:

myMethod<T>(Expression<Func<T,bool>> where)

example after comment:

consider the following type:

you see there are three properties where the name is of type string and id is of type int. now if we wrap our database context in a service like this

public class MyTypeOfXService
{
    private DataDataContext Context;
    public MyTypeOfXService()
    {
        Context = new DataDataContext("example code");
    }

    public IQueryable<MyTypeOfX> GetTypeOfX(Expression<Func<MyTypeOfX, bool>> where)
    {
        return this.Context.MyTypeOfXes.Where(where);
    }
}

in our get method there is an Expression parameter that takes two generics, the first is our type x and the second is a boolean. The advantage of this approach is that we can abstract all the data context creation and only express an where clause in our code see final piece of code:

class Program
{
    static void Main(string[] args)
    {
        var service = new MyTypeOfXService();

        var queryById = service.GetTypeOfX((mytype) => mytype.Id == 1);
        var queryByName = service.GetTypeOfX((mytype) => mytype.Name == "MyName");
        var queryByName = service.GetTypeOfX((mytype) => mytype.Name == "MyName" && mytype.Id == 1);
    }
}

as you can see, we can build a where clause on any property or combination of properties.