I have two lists I would like to compare them for updated/modified columns. Compare 2 Lists of the same class and show the different values in a new list I would like to do this using linq. The only problem is I am dealing with a lot of columns, over excess of 30 columns in each. Any suggestions would be of great help...
//In Dal
List<PartnerAndPartnerPositionEntity> GetAllPartnerAndPartnerPositionOldDB(int modelId);
List<PartnerAndPartnerPositionEntity> GetAllPartnerAndPartnerPosition(int modelId);
//BL
//get from new db
var list1= _partnerDAL.GetAllPartnerAndPartnerPosition(modelId);
//get from old db
var list2= _partnerDAL.GetAllPartnerAndPartnerPositionOldDB(modelId);
Let's assume that:
PartnerAndPartnerPositionEntity
class contains a property named Id
that represents the unique key of an item Given the above you can:
Get all properties of your type
var properties = typeof(PartnerAndPartnerPositionEntity).GetProperties();
Join the two lists on the Id
property and iterate through the properties to see which one has changed:
var list = list1.Join(list2,
x => x.Id,
y => y.Id,
(x, y) => Tuple.Create(x, y))
.ToList();
list.Foreach(tuple =>
{
foreach(var propertyInfo in properties)
{
var value1 = propertyInfo.GetValue(tuple.Item1, null);
var value2 = propertyInfo.GetValue(tuple.Item2, null);
if(value1 != value2)
Console.WriteLine("Item with id {0} has different values for property {1}.",
tuple.Item1,Id, propertyInfo.Name);
}
});
Well, if you want to avoid doing it the boring and tedious way, you need to use reflection to dynamically get the class members then get their values for each instance. See C# Reflection - Get field values from a simple class for the code.
There...this will generate new IL!
public static class EqualityHelper
{
private ConcurrentDictionary<Type, object> _cache = new ConcurrentDictionary<Type, object>();
public bool AreEqual<T>(T left, T right)
{
var equality = (Func<T,T,bool>)_cache.GetOrAdd(typeof(T), CreateEquality<T>());
return equality(left, right);
}
private Func<T, T, bool> CreateEquality<T>()
{
var left = Expression.Parameter(typeof(T));
var right = Expression.Parameter(typeof(T));
var properties = from x in typeof(T).GetProperties()
where x.GetIndexParameters().Any() == false
select x;
var expressions = from p in properties
select Expression.Equal(
Expression.Property(left, p),
Expression.Property(right, p));
var body = expressions.Aggregate(Expression.AndAlso);
var lambda = Expression.Lambda<Func<T,T,bool>>(body, new [] {left, right});
return lambda.Compile();
}
}
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