c#中var的用法 - 爱码网

一、VAR 是3.5新出的一个定义强类型方式定义变量完全一样。

四、var 关键字的常见用途是用于构造函数调用表达式。

使用 var则不能在变量声明和对象实例化中重复类型名称，如下面的示例所示：

var xs = new List<int>();

new 表达式作为替代方法：

List<int> xs = new();
List<int>? ys = new();

请注意，在示例 #2 中，foreach 迭代变量 item 必须也为隐式类型。

// Example #1: var is optional when
// the select clause specifies a string
string[] words = { "apple", "strawberry", "grape", "peach", "banana" };
var wordQuery = from word in words
                where word[0] == 'g'
                select word;

// Because each element in the sequence is a string,
// not an anonymous type, var is optional here also.
foreach (string s in wordQuery)
{
    Console.WriteLine(s);
}

// Example #2: var is required because
// the select clause specifies an anonymous type
var custQuery = from cust in customers
                where cust.City == "Phoenix"
                select new { cust.Name, cust.Phone };

// var must be used because each item
// in the sequence is an anonymous type
foreach (var item in custQuery)
{
    Console.WriteLine("Name={0}, Phone={1}", item.Name, item.Phone);
}

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