C# LINQ Aggregate的用法小结

public static TResult Aggregate<TSource, TAccumulate, TResult>(
    this IEnumerable<TSource> source,
    TAccumulate seed,
    Func<TAccumulate, TSource, TAccumulate> func,
    Func<TAccumulate, TResult> resultSelector
)

int[] numbers = { 1, 2, 3, 4, 5 };
int sum = numbers.Aggregate((a, b) => a + b);
// 结果: 15

int[] numbers = { 1, 2, 3, 4, 5 };
int sum = numbers.Aggregate(10, (a, b) => a + b);
// 结果: 25 (10 + 1 + 2 + 3 + 4 + 5)

string[] words = { "Hello", "World", "!" };
string result = words.Aggregate((a, b) => a + " " + b);
// 结果: "Hello World !"

var products = new List<Product>
{
    new Product { Name = "A", Price = 10 },
    new Product { Name = "B", Price = 20 },
    new Product { Name = "C", Price = 30 }
};

decimal totalPrice = products.Aggregate(0m, 
    (sum, product) => sum + product.Price);
// 结果: 60

string[] words = { "apple", "banana", "cherry" };
string result = words.Aggregate(
    seed: 0,  // 初始值
    func: (length, word) => length + word.Length,  // 累加每个单词的长度
    resultSelector: total => $"总字符数: {total}"  // 转换最终结果
);
// 结果: "总字符数: 17"

// 处理空序列
var emptyList = new List<int>();
int result = emptyList.DefaultIfEmpty(0)
                     .Aggregate((a, b) => a + b);

try
{
    var result = collection.Aggregate((a, b) => a + b);
}
catch (InvalidOperationException)
{
    // 处理空序列异常
}