1. SingletonPattern
入门示例
定义单例模式，在需要定义的类上加上[SingletonPattern]特性，并保证类加上partial修饰符
[SingletonPattern]
public partial class Service1
{
public void SayHello(string name)
{
Console.WriteLine($"Hello,{name}");
}
}
上面的代码，因为定义了[SingletonPattern]特性，SourceGenerator会自动帮我们生成以下代码
partial class Service1
{
private static readonly Lazy<Service1> LazyInstance = new Lazy<Service1>(() => new Service1(), true);
private Service1() { }
public static Service1 Instance => LazyInstance.Value;
}
使用的代码
Service1.Instance.SayHello("Zhang");
自定义单例属性名称
可以在[SingletonPattern]里面加上InstancePropertyName，用于指定单例属性的名称。
[SingletonPattern(InstancePropertyName = "Default")]
public partial class Service2
{
public void SayHello(string name)
{
Console.WriteLine($"Hello,{name}");
}
}
使用的代码
Service2.Default.SayHello("Zhang");
2. AutoConstructor
入门示例
需要在自动生成构造函数的类上面加上[AutoConstructor], 并确保类加上partial修饰符，这样就会生成一个包含类内部所有字段和属性的构造函数。
[AutoConstructor]
public partial class Demo1
{
private string strValue;
private int intValue;
}
应用了[AutoConstructor]后，SourceGenerator会自动生成以下代码片段
partial class Demo1
{
public Demo1(string strValue, int intValue)
{
this.strValue = strValue;
this.intValue = intValue;
}
}
可以看到生成的代码相当于我们手写的代码，并且自动把字段赋值成构造函数传入的值了。
使用的代码如下
var demo = new Demo1("val1", 1);
使用属性
对于自动实现的属性，AutoConstructor同样适用。这里要注意的是必须是自动实现的属性，如果属性包含了代码定义，则会忽略改属性。
[AutoConstructor]
public partial class Demo2
{
public string StrValue { get; set; }
public int IntValue { get; set; }
}
使用的代码
var demo = new Demo2("val2", 2);
NullCheck
```csharp
[AutoConstructor(NullCheck = true)]
public partial class Demo3
{
private string strValue;
private int intValue;
}
上述代码对应生成的代码如下
partial class Demo3
{
public Demo3(string strValue, int intValue)
{
this.strValue = strValue ?? throw new System.ArgumentNullException(nameof(strValue));
this.intValue = intValue;
}
}
当使用以下代码调用时，会抛出System.ArgumentNullException的异常
var demo = new Demo3(null, 1);
忽略字段
如果想要指定某个字段或者属性不通过构造函数赋值，那么可以在该字段或属性上面使用AutoConstructorIgnore特性
[AutoConstructor]
public partial class Demo4
{
private string strValue;
[AutoConstructorIgnore]
private int intValue;
}
上述代码生成的构造函数就会忽略intValue字段的赋值。
partial class Demo4
{
public Demo4(string strValue)
{
this.strValue = strValue;
}
}
初始化函数
允许我们为每个类定义一个无参的初始化函数，我们需要在这个函数上加上[AutoConstructorInitialize]特性，那么生成的构造函数会自动帮我们去调用这个初始化函数。
例如以下代码
[AutoConstructor]
public partial class Demo5
{
private string strValue;
private int intValue;
[AutoConstructorInitialize]
private void MyInitLogic()
{
Console.WriteLine("instance is creating.");
}
}
生成的构造函数如下
partial class Demo5
{
public Demo5(string strValue, int intValue)
{
this.strValue = strValue;
this.intValue = intValue;
this.MyInitLogic();
}
}
一般情况下，[AutoConstructorInitialize]都会结合[AutoConstructorIgnore]，完成自定义的初始化逻辑。
依赖注入
在使用依赖注入的场景，使用AutoConstructor可以帮助我们减少写构造函数的麻烦。例如以下的代码，如果可以从Dependency Injection容器中获取到IService1和IService2的实例的话，那么从容器中获取Demo6Service则可以正常工作。
public interface IService1
{
void Action1();
}
public interface IService2
{
void Action2();
}
[AutoConstructor]
public partial class Demo6Service
{
private readonly IService1 service1;
private readonly IService2 service2;
public void Action()
{
service1.Action1();
service2.Action2();
}
}
继承
```csharp
[AutoConstructor]
public partial class Demo7Parent
{
private string strValue;
}
[AutoConstructor]
public partial class Demo7Child: Demo7Parent
{
private int intValue;
}
自动生成的代码如下
partial class Demo7Parent
{
public Demo7Parent(string strValue)
{
this.strValue = strValue;
}
}
partial class Demo7Child
{
public Demo7Child(string strValue, int intValue)
: base(strValue: strValue)
{
this.intValue = intValue;
}
}
3. Mapper
入门示例
假如我们有两个User的类，结构相似，我们需要把其中的一个对象转换成另一个对象。
public record UserDto
{
public Guid Id { get; set; }
public string Name { get; set; }
public int Age { get; set; }
}
public record UserEntity
{
public Guid Id { get; set; }
public string Name { get; set; }
public int Age { get; set; }
}
只需要在需要转换的类上面定义[Mapper(typeof(UserEntity), typeof(UserDto))]，当定义了以上Mapper特性后，SourceGenerator会自动给UserEntity增加一个To的泛型方法。使用这个泛型方法我们可以把UserEntity转换为UserDto 对象。
[Mapper(typeof(UserEntity), typeof(UserDto))]
internal class Program
{
static void Main(string[] args)
{
var user = new UserEntity { Age = 10, Name = "zhangsan", Id = Guid.NewGuid() };
var userDto = user.To<UserDto>();
Console.WriteLine(userDto);
}
}
以上代码生成的核心代码如下
private static global::Mapper.Demo.UserDto ToMapper_Demo_UserDto(this global::Mapper.Demo.UserEntity source)
{
if (source == null) return default;
return new global::Mapper.Demo.UserDto
{
Id = source.Id,
Name = source.Name,
Age = source.Age,
};
}
public static T To<T>(this global::Mapper.Demo.UserEntity source) where T : new()
{
if (source == null) return default;
if (typeof(T) == typeof(global::Mapper.Demo.UserDto))
{
return (T)(object)ToMapper_Demo_UserDto(source);
}
throw new NotSupportedException($"Can not convert '{typeof(global::Mapper.Demo.UserEntity)}' to '{typeof(T)}'.");
}
单个对象存在嵌套对象
[Mapper(typeof(UserEntity), typeof(UserDto))]
internal class Program
{
static void Main(string[] args)
{
var user = new UserEntity { Age = 10, Name = "zhangsan", City = new CityEntity { Name = "Xi'an", Province = "Shannxi" };
var userDto = user.To<UserDto>();
Console.WriteLine(userDto);
}
}
public record UserEntity
{
public Guid Id { get; set; }
public string Name { get; set; }
public int Age { get; set; }
public CityEntity City { get; set; }
}
public record CityEntity
{
public Guid Id { get; set; }
public string Name { get; set; }
public string Province { get; set; }
}
public record UserDto
{
public string Name { get; set; }
public int Age { get; set; }
public CityDto City { get; set; }
}
public record CityDto
{
public string Name { get; set; }
public string Province { get; set; }
}
上面的代码运行输出如下，可以看见City属性也被正确的填充了，因为我们定义了[Mapper(typeof(UserEntity), typeof(UserDto))]，这样会自动尝试帮我们映射City属性，即使两个的类型不同。
UserDto { Name = zhangsan, Age = 10, City = CityDto { Name = xi'an, Province = shannxi } }
生成的核心代码如下
private static global::Mapper.Demo.UserDto ToMapper_Demo_UserDto(this global::Mapper.Demo.UserEntity source)
{
if (source == null) return default;
return new global::Mapper.Demo.UserDto
{
Name = source.Name,
Age = source.Age,
City = source.City == null ? default : new global::Mapper.Demo.CityDto
{
Name = source.City.Name,
Province = source.City.Province,
},
};
}
导航属性
有时候，目标对象会展示源对象的一些属性，例如以下的例子
[Mapper(typeof(UserEntity), typeof(UserDto))]
internal class Program
{
static void Main(string[] args)
{
var user = new UserEntity { Age = 10, Name = "zhangsan", City = new CityEntity { Name = "xi'an", Province = "shannxi" } };
var userDto = user.To<UserDto>();
Console.WriteLine(userDto);
}
}
public record UserEntity
{
public Guid Id { get; set; }
public string Name { get; set; }
public int Age { get; set; }
public CityEntity City { get; set; }
}
public record CityEntity
{
public Guid Id { get; set; }
public string Name { get; set; }
public string Province { get; set; }
}
public record UserDto
{
public string Name { get; set; }
public int Age { get; set; }
public Guid CityId { get; set; }
public string CityName { get; set; }
public string CityProvince { get; set; }
}
生成的核心代码如下
private static global::Mapper.Demo.UserDto ToMapper_Demo_UserDto(this global::Mapper.Demo.UserEntity source)
{
if (source == null) return default;
return new global::Mapper.Demo.UserDto
{
Name = source.Name,
Age = source.Age,
CityId = source.City.Id,
CityName = source.City.Name,
CityProvince = source.City.Province,
};
}
单个对象存在嵌套集合对象
[Mapper(typeof(UserEntity), typeof(UserDto))]
internal class Program
{
static void Main(string[] args)
{
var user = new UserEntity { Age = 10, Name = "zhangsan", Cities = new List<CityEntity> { new CityEntity { Name = "xi'an", Province = "shannxi" } } };
var userDto = user.To<UserDto>();
Console.WriteLine(userDto);
}
}
public record UserEntity
{
public Guid Id { get; set; }
public string Name { get; set; }
public int Age { get; set; }
public List<CityEntity> Cities { get; set; }
}
public record CityEntity
{
public Guid Id { get; set; }
public string Name { get; set; }
public string Province { get; set; }
}
public record UserDto
{
public string Name { get; set; }
public int Age { get; set; }
public CityDto[] Cities { get; set; }
}
public record CityDto
{
public string Name { get; set; }
public string Province { get; set; }
}
生成的核心代码如下
private static global::Mapper.Demo.UserDto ToMapper_Demo_UserDto(this global::Mapper.Demo.UserEntity source)
{
if (source == null) return default;
return new global::Mapper.Demo.UserDto
{
Name = source.Name,
Age = source.Age,
Cities = source.Cities == null ? default : source.Cities.Select(p => p == null ? default(global::Mapper.Demo.CityDto) : new global::Mapper.Demo.CityDto
{
Name = p.Name,
Province = p.Province,
}).ToArray(),
};
}
转换集合对象
也可以一次性转换集合对象，例如下面的例子
[Mapper(typeof(UserEntity), typeof(UserDto))]
internal class Program2
{
static void Main(string[] args)
{
var userList = new List<UserEntity>
{
new UserEntity { Age = 10, Name = "zhangsan", Id = Guid.NewGuid() }
};
var userDtoArray = userList.To<UserDto>().ToArray();
Console.WriteLine(userDtoArray);
}
}
public record UserDto
{
public Guid Id { get; set; }
public string Name { get; set; }
public int Age { get; set; }
}
public record UserEntity
{
public Guid Id { get; set; }
public string Name { get; set; }
public int Age { get; set; }
}
核心代码如下
public static IEnumerable<T> To<T>(this IEnumerable<global::Mapper.Demo.UserEntity> source) where T : new()
{
if (typeof(T) == typeof(global::Mapper.Demo.UserDto))
{
return (IEnumerable<T>)source?.Select(p => p.ToMapper_Demo_UserDto());
}
throw new NotSupportedException($"Can not convert '{typeof(global::Mapper.Demo.UserEntity)}' to '{typeof(T)}'.");
}