ef linq join
时间: 2023-07-24 10:34:48 浏览: 71
LINQ Join操作是用于将两个序列中的元素进行匹配,然后将它们合并为一个新的序列。它与SQL语句中的JOIN操作类似。Join操作需要两个输入源,通常是两个集合或表格,以及一个键选择器,它用于指定用于匹配元素的键。Join操作返回一个新的序列,其中包含匹配的元素对。
下面是一个简单的LINQ Join操作示例:
```csharp
var customers = new List<Customer>
{
new Customer {Id = 1, Name = "Alice", City = "New York"},
new Customer {Id = 2, Name = "Bob", City = "Chicago"},
new Customer {Id = 3, Name = "Charlie", City = "Los Angeles"}
};
var orders = new List<Order>
{
new Order {Id = 1, CustomerId = 1, ProductName = "Product A"},
new Order {Id = 2, CustomerId = 2, ProductName = "Product B"},
new Order {Id = 3, CustomerId = 2, ProductName = "Product C"},
new Order {Id = 4, CustomerId = 3, ProductName = "Product D"}
};
var customerOrders = from customer in customers
join order in orders on customer.Id equals order.CustomerId
select new { CustomerName = customer.Name, ProductName = order.ProductName };
foreach (var item in customerOrders)
{
Console.WriteLine($"Customer Name: {item.CustomerName}, Product Name: {item.ProductName}");
}
```
在上面的示例中,我们使用Join操作将客户和订单集合中的元素进行匹配,并将匹配的结果放入一个新的匿名对象中。最后,我们通过foreach循环遍历新的序列并输出结果。
希望这个例子能够帮助你理解LINQ Join操作的工作原理。