C#中的dynamic与var区别对比分析

var name = "byteflow";   // 编译器将name推断为string类型
var age = 25;          // 编译器将age推断为int类型

string name = "byteflow";
int age = 25;

var number = 10;
// number = "ten";  // 编译错误！int类型不能赋值为string

dynamic value = 100;
value = "现在我是字符串";  // 完全合法！
value = new List<int>();  // 也没问题！

dynamic obj = GetSomeObject();  // 我们不确定返回什么类型
obj.DoSomething();              // 编译通过，运行时决定能否调用

var dictionary = new Dictionary<string, List<Customer>>();
// 比 Dictionary<string, List<Customer>> dictionary = new Dictionary<string, List<Customer>>(); 更简洁

var person = new { Name = "byteflow", Age = 25 };

var results = from c in customers where c.City == "北京" select c;

dynamic excel = Activator.CreateInstance(Type.GetTypeFromProgID("Excel.Application"));
excel.Visible = true;

dynamic jsonData = JsonConvert.DeserializeObject(jsonString);
string name = jsonData.Name;  // 无需预先知道JSON结构

dynamic instance = Activator.CreateInstance(someType);
instance.SomeMethod();  // 比反射代码简洁

void ProcessObject(Person person)
{
    var name = person.Name;  // 编译器知道这是string类型
    var age = person.Age;    // 编译器知道这是int类型
    Console.WriteLine($"{name}今年{age}岁");
}

void ProcessAnyObject(dynamic obj)
{
    try {
        var info = $"{obj.Name}今年{obj.Age}岁";
        Console.WriteLine(info);
    }
    catch (RuntimeBinderException) {
        Console.WriteLine("对象不包含所需属性");
    }
}