my_note

1.C# $ 内插字符串  Console.WriteLine($"The value of pi is {Math.PI}");  替代string.format

2. switch  的新写法 colorBand 是枚举

public static RGBColor FromRainbow(Rainbow colorBand) =>
colorBand switch
{
Rainbow.Red => new RGBColor(0xFF, 0x00, 0x00),
Rainbow.Orange => new RGBColor(0xFF, 0x7F, 0x00),
Rainbow.Yellow => new RGBColor(0xFF, 0xFF, 0x00),
Rainbow.Green => new RGBColor(0x00, 0xFF, 0x00),
Rainbow.Blue => new RGBColor(0x00, 0x00, 0xFF),
Rainbow.Indigo => new RGBColor(0x4B, 0x00, 0x82),
Rainbow.Violet => new RGBColor(0x94, 0x00, 0xD3),
_ => throw new ArgumentException(message: "invalid enum value", paramName: nameof(colorBand)),
};

public static decimal ComputeSalesTax(Address location, decimal salePrice) =>
location switch
{
{ State: "WA" } => salePrice * 0.06M,
{ State: "MN" } => salePrice * 0.75M,
{ State: "MI" } => salePrice * 0.05M,
// other cases removed for brevity...
_ => 0M
}; //属性模式

List<modelTest> list = new List<modelTest>();
list.Add(new modelTest {id=1, name="aaa", address="aaaaaa" });
list.Add(new modelTest { id = 2, name = "bbb", address = "bbbbbb" });
list.Add(new modelTest { id = 3, name = "ccc", address = "cccccc" });
list.Add(new modelTest { id = 4, name = "ddd", address = "dddddd" });
list.Add(new modelTest { id = 5, name = "eee", address = "eeeeee" });

var aa= list.Where(x=>x.name== "aaa").ToList();
var bb = list.Where(x => x.name == "bbbb");
var dd = list.Where(x => x.name == "bbbb").ToList();不会报错 不为null  但是count为0
var eecc = list.Where(x => x.name == "bbbb").First(); 序列为空 报错
var eecctt = list.Where(x => x.name == "bbbb").ToList().First(); 序列为空 报错
var dddddd = list.Where(x => x.name == "bbbb").FirstOrDefault(); 不会报错 为空 返回null
var ccc= "";

<<<<<<<<<<oracle 创建别名>>>>>>>>>>>

　在当前数据库里面创建  输入需要连接的数据库的账号信息 。然后直接在当前数据库里面调用

dbeaver 数据库工具

//json类型数据接收的写法
public string XxxxxxSync([FromBody] object content)
{
List<TestData> list = JsonConvert.DeserializeObject<List<xxxx>>(content.ToString());
}

委托在.net core  不支持begininvoke

内聚：指一个功能模块内部所有内容之间的关联度、相关性和紧密度

对于关联性很强的内容，将其放在一个模块的内部

耦合：

不同功能模块之间的依赖关系

高内聚 低耦合

这是软件开发的核心思想，绝对内聚和彻底无耦合是不存在的。

调试压缩过的js  source map

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写事务最基本的 try catch   异常的时候要回滚。一定要有 commit 和rollback