/// <summary>
/// Compares two collections of objects of type <typeparamref name="T"/>.
/// </summary>
/// <param name="list1">The first collection</param>
/// <param name="list2">The second collection</param>
/// <returns>A list of <see cref="ObjectComparison{T}"/> records representing the results of the comparison of the two collections</returns>
public IReadOnlyCollection <ObjectComparison <T> > Compare(IReadOnlyCollection <T> list1, IReadOnlyCollection <T> list2)
{
IDictionary <string, T> dict1, dict2;
try
{
dict1 = list1.ToDictionary(_ => this.keyProvider.GetKey(_));
}
catch (ArgumentException)
{
throw new ComparisonException($"Comparer <{this.Name}> by key <{this.keyProvider.Name}>: List1 contains duplicate values by key!");
}
try
{
dict2 = list2.ToDictionary(_ => this.keyProvider.GetKey(_));
}
catch (ArgumentException)
{
throw new ComparisonException($"Comparer <{this.Name}> by key <{this.keyProvider.Name}>: List2 contains duplicate values by key!");
}
var resultList = new List <ObjectComparison <T> >();
foreach (var kvp in dict1)
{
var item1 = kvp.Value;
ObjectComparison <T> comparison;
if (!dict2.TryGetValue(kvp.Key, out T item2))
{
this.equalityComparer.Equals(item1, null, out List <Difference> differentProperties);
comparison = ObjectComparison <T> .OnlyItem1(kvp.Key, item1, differentProperties);
}
else
{
comparison = DeepCompare(kvp.Key, item1, item2);
}
resultList.Add(comparison);
}
foreach (var kvp in dict2)
{
var item2 = kvp.Value;
if (dict1.ContainsKey(kvp.Key))
{
continue;
}
this.equalityComparer.Equals(null, item2, out List <Difference> differentProperties);
var comparison = ObjectComparison <T> .OnlyItem2(kvp.Key, item2, differentProperties);
resultList.Add(comparison);
}
return(resultList);
}
/// <summary>
/// Uses the equality comparer to compare two objects of the collection in order to identify whether they are equal or
/// different by some property.
/// </summary>
/// <param name="key">The objects key</param>
/// <param name="item1">The first item</param>
/// <param name="item2">The second item</param>
/// <returns>An instance of <see cref="ObjectComparison{T}"/> that represents the result of the comparison</returns>
private ObjectComparison <T> DeepCompare(string key, T item1, T item2)
{
var areEqual = this.equalityComparer.Equals(item1, item2, out List <Difference> differentProperties);
if (areEqual)
{
return(ObjectComparison <T> .Equals(key, item1, item2));
}
return(ObjectComparison <T> .MatchingButDifferent(key, item1, item2, differentProperties));
}
