linq func

gistfile1.cs

In my mapping class, the method signature would be similar to this:

public abstract class FluentMap<TEntity> {

  protected MyMapStuff Map(Expression<Func<TEntity, object>> propertyExpression){
      return this;
      }
}
      
My Expression takes func where TEntity is a class such as ‘MyEntity’, and the return type is object, thus covering all various returns value seeing as every class inherit from System.Object.

Now, to extract the information I may need out of that expresion, I can use

private PropertyPart ExtractMemberInfo(Expression<Func<TEntity, object>> propertyExpression)
        {
            var memberExpression = propertyExpression.Body as MemberExpression;
            if (memberExpression != null)
            {
                return new PropertyMapInfo
                           {
                               Name = propertyExpression.Name,
                               ReflectedType = memberExpression.Member.ReflectedType,
                               PropertyType = memberExpression.Type
                           };
            }
            throw new ArgumentException(string.Format("In the expression {0}, \"{1}\" is not property of the entity", propertyExpression, propertyExpression.Name));
        }

class PropertyMapInfo
        {
            public string Name { get; set; }
            public Type ReflectedType { get; set; }
            public Type PropertyType { get; set; }
        }
Now I can do:

public class MyEntityMap: FluentMap<MyEntity>{
  public MyEntityMap(){
      Map(e=> e.Name);
  }
}
Inside my ‘Map’ method, I can implement the appropriate ORM logic.