Question

I have a working setup which is not strongly typed and relies on reflection.

I have a class, say

class Person{

    public string FirstName {get ; set;}
    public string LastName {get; set;}
    public int Age {get; set;}
    ...  
    // some more public properties
}

and

class CellInfo {
     public string Title {get; set;}
     public string FormatString {get; set;}
}

and I have a dictionary like this

Dictionary<string, CellInfo> fields = new Dictionary<string, CellInfo>();
fields.Add("FirstName", new CellInfo {Title = "First Name", FormatString = "Foo"});
fields.Add("LastName", new CellInfo {Title = "Last Name", FormatString = "Bar"});

It’s a simple dictionary with property Names and some info about them.
I pass the dictionary to another module that processes Person instances and I do

Dictionary<string, CellInfo> fields = SomeMethodToGetDictionary();
foreach(Person p in someCollection)
{
    foreach(var field in fields)
    { 
       object cellValue = type(Person).GetProperty(field.Key).GetValue(p, null);
       // use cellValue and info on field from field.Value somewhere.
       ...
    }
 }

This method of passing the string for field name and using reflection works, but I was wondering if there is a strongly-typed method of doing this.

What I had in mind was having a property that stored a linq expression, something like this

fields.Add("FirstName", new CellInfo 
                   {
                      Title = "First Name", 
                      FormatString = "Foo",
                      EvalExpression = p => p.FirstName
                   });

and during usage, somehow use the EvalExpression on a person object and get the property value. I have no clue where to begin or what the syntax would be like to have a property like this that’s evaluateable. I’m new to function delegates and expression trees that I don’t even know the right keywords to search for. Hope my description is clear; if not, let me know and I’ll details as necessary.
Any assistance would much appreciated.

Answer 1

You can try something like this to not have to code the property names as strings if this is what you mean by saying strongly typed:

class CellInfo<T>
{
    public string Title { get; set; }
    public string FormatString { get; set; }
    public Func<T, object> Selector { get; set; }
}

Dictionary<string, CellInfo<Person>> dict = new Dictionary<string, CellInfo<Person>>();

dict.Add("LastName", new CellInfo<Person> { Selector = p => p.LastName });
dict.Add("Age", new CellInfo<Person> { Selector = p => p.Age });

foreach (Person p in someCollection)
{
    foreach (var cellInfo in dict)
    {
        object value = cellInfo.Value.Selector(p);
    }
}