C# IEqualityComparer类型参数写法

最近在使用Union、Except时，由于默认的对比不太好使，所以需要自定义对比器，下面附上代码。

class MaterialListComparer : IEqualityComparer<WonderManager.Basal.Material.Domain.Material>
    {
        public bool Equals(WonderManager.Basal.Material.Domain.Material x, WonderManager.Basal.Material.Domain.Material y)
        {
            if (Object.ReferenceEquals(x, y)) return true;
            if (Object.ReferenceEquals(x, null) || Object.ReferenceEquals(y, null))
                return false;
            return x.MaterialCode == y.MaterialCode;
        }

        public int GetHashCode(WonderManager.Basal.Material.Domain.Material model)
        {
            if (Object.ReferenceEquals(model, null)) return 0;

            int hashProductName = model.MaterialCode == null ? 0 : model.MaterialCode.GetHashCode();

            return hashProductName;
        }
    }