在两个IEnumerable集合中添加项的值

包含重复键的案例的最通用解决方案可以使用GroupBy和Sum LINQ方法实现:

var result = firstCollection
    .Concat(secondCollection)
    .GroupBy(x => x.Name)
    .Select(g => new Foo { Name = g.Key, Value = g.Sum(f => f.Value) });
    // Foo is an example of your element class. You can use anonymous classes
    //.Select(g => new { Name = g.Key, Value = g.Sum(f => f.Value) });

该解决方案的算法复杂度为O(n).

如果您希望获得最大性能,可以使用序数字符串比较:

var result = firstCollection
    .Concat(secondCollection)
    .GroupBy(x => x.Name, x => x, StringComparer.Ordinal)
    .Select(g => new Foo { Name = g.Key, Value = g.Sum(f => f.Value) });