Merge branch 'master' into 'master'

Master

See merge request csdn/skill_tree_dotnet!5

data/1..NET初阶/2.C#语法/3.C#字符串格式设置/StringFormatting.md

-# 在C#中执行基本字符串格式设置
+# 在C#中执行基本字符串格式设置
 
 System.String是一个类，专门用于存储字符串，允许对字符串进行许多操作。由于这种数据类
 型非常重要，C#提供了它自己的关键字和相关的语法，以便于使用这个类来轻松地处理字符串。 
@@ -8,8 +8,8 @@ String 源码网址: https://referencesource.microsoft.com/#mscorlib/system/stri
 
 ```csharp
 string message1 = "Hello";	// return "Hello"
-message1 += ", CodeChina";	// return "Hello, CodeChina"
-string message2 = message1 + "!";	//return "Hello, CodeChina!"
+message1 += ", CSDN";	// return "Hello, CSDN"
+string message2 = message1 + "!";	//return "Hello, CSDN!"
 ```
 
 C#还允许使用类似于索引器的语法来提取指定的字符:
@@ -47,13 +47,13 @@ string str1 = $"6{count}6";	// return "666"
 string str2 = @"6\r6\n6";	//return "6\r6\n6"
 ```
 
-以下程序中，不能使str3等于`"Hello, CodeChina!"`的是：
+以下程序中，不能使str3等于`"Hello, CSDN!"`的是：
 
 ## 答案
 
 ```csharp
 var str1 = "Hello, ";
-var str2 = "CodeChina!";
+var str2 = "CSDN!";
 var str3 = "str1" + "str2";
 ```
 
@@ -63,7 +63,7 @@ var str3 = "str1" + "str2";
 
 ```csharp
 var str1 = "Hello, ";
-var str2 = "CodeChina!";
+var str2 = "CSDN!";
 var str3 = str1 + str2;
 ```
 
@@ -71,7 +71,7 @@ var str3 = str1 + str2;
 
 ```csharp
 var str1 = "Hello";
-var str2 = "CodeChina";
+var str2 = "CSDN";
 var str3 = string.Format("{0}, {1]!", str1, str2);
 ```
 
@@ -79,7 +79,7 @@ var str3 = string.Format("{0}, {1]!", str1, str2);
 
 ```csharp
 var str1 = "Hello, ";
-var str2 = "CodeChina!";
+var str2 = "CSDN!";
 var str3 = string.Concat(str1, str2);
 ```
 

data/1..NET初阶/3.C#特性/1.C#3.0特性/ImplicitType.json

+{
+  "type": "code_options",
+  "author": "Gao996",
+  "source": "ImplicitType.md",
+  "exercise_id": "41982620620243ef956a14e95c584d2d",
+  "notebook_enable": false
+}
\ No newline at end of file

data/1..NET初阶/3.C#特性/1.C#3.0特性/ImplicitType.md

+# C# 3.0 特性 隐式类型本地变量
+
+从C# 3.0 开始，在方法范围内声明的变量可以具有隐式“类型”var。隐式类型本地变量为强类型，就像用户已经自行声明该类型，但编译器决定类型一样。
+
+```var i = “Hello CSDN！”;```看这句代码，在下列选项中i的类型是：
+
+## 答案
+
+```csharp
+string
+```
+
+## 选项
+
+### A
+
+```csharp
+int
+```
+
+### B
+
+```csharp
+char
+```
+
+### C
+
+```csharp
+double
+```
\ No newline at end of file

data/1..NET初阶/3.C#特性/1.C#3.0特性/ObjectAndCollectionInitializers.json

+{
+  "type": "code_options",
+  "author": "Gao996",
+  "source": "ObjectAndCollectionInitializers.md",
+  "exercise_id": "7bb7e2531e7a426cbd731720fa33d0ba",
+  "notebook_enable": false
+}
\ No newline at end of file

data/1..NET初阶/3.C#特性/1.C#3.0特性/ObjectAndCollectionInitializers.md

+# C# 3.0 特性 对象和集合初始值设定项
+
+使用对象初始值设定项，你可以在创建对象时向对象的任何可访问字段或属性分配值，而无需调用后跟赋值语句行的构造函数。 比如下面的Cat类，以往创建对象可能
+```csharp 
+Cat cat = new Cat();
+cat.Name = "Tom";
+cat.Age = 10;
+```
+当然可以直接为对象设置初始值，这样可以简化对象的构造，如下例子：
+
+```csharp
+public class Cat
+{
+    // 自动实现的属性
+    public int Age { get; set; }
+    public string Name { get; set; }
+
+    public Cat()
+    {
+    }
+
+    public Cat(string name)
+    {
+        this.Name = name;
+    }
+}
+```
+```csharp
+Cat cat = new Cat { Age = 10, Name = "Fluffy" };
+Cat sameCat = new Cat("Fluffy"){ Age = 10 };
+```
+上面这段代码示例了使用具有命名类型Cat的对象初始值设定项以及如何调用无参数构造函数。当然也可以为匿名类型设置初始值：
+```csharp
+var testA = new { name = "Gao", age = 996 };
+```
+下面是一个List集合的初始化例子：
+```csharp
+List<int> digits = new List<int> { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }; 
+```
+除了分配字段和属性外，对象初始值设定项还可以设置索引器，如下例子：
+```csharp
+public class MatrixTest
+{
+    private readonly double[,] storage = new double[3, 3];
+
+    public double this[int row, int column]
+    {
+        get { return storage[row, column]; }
+        set { storage[row, column] = value; }
+    }
+}
+```
+```csharp
+var identity = new MatrixTest()
+{
+    [0, 0] = 1.0,
+    [0, 1] = 0.0,
+    [0, 2] = 0.0,
+
+    [1, 0] = 0.0,
+    [1, 1] = 1.0,
+    [1, 2] = 0.0,
+
+    [2, 0] = 0.0,
+    [2, 1] = 0.0,
+    [2, 2] = 1.0
+};
+```
+
+在了解了对象和集合初始值的设定之后，实现对Dictionary初始值设定，以下选项错误的是：
+
+## 答案
+
+```csharp
+var numbers = new Dictionary<int, string>()
+{
+    7 = "seven",
+    9 = "nine",
+    13 = "thirteen"
+};
+```
+
+## 选项
+
+### A
+
+```csharp
+var numbers = new Dictionary<int, string>()
+{
+    [1] = "one",
+    [9] = "nine",
+    [13] = "thirteen"
+};
+```
+
+### B
+
+```csharp
+var numbers = new Dictionary<int, string>()
+{
+    {19, "nineteen" },
+    {23, "twenty-three" },
+    {42, "forty-two" }
+};
+```
+
+### C
+
+```csharp
+var numbers = new Dictionary<int, string>()
+{
+};
+```
\ No newline at end of file

data/1..NET初阶/3.C#特性/1.C#3.0特性/PartialMethod.json

+{
+  "type": "code_options",
+  "author": "Gao996",
+  "source": "PartialMethod",
+  "exercise_id": "4a743fa6bf5e49cf8fff28ed0f9e6bef",
+  "notebook_enable": false
+}
\ No newline at end of file

data/1..NET初阶/3.C#特性/1.C#3.0特性/PartialMethod.md

+# C# 3.0 特性 分部方法
+
+分部方法在分部类型的一部分中定义了签名，并在该类型的另一部分中定义了实现。比如WPF和WinForm的窗体就是用partial关键字定义的分部类，一部分代码可以实现控件的初始化，一部分可以去实现具体方法等。
+
+```csharp
+partial class PartialClassTest
+{
+    readonly string str = "Hello CSDN!";
+
+    partial void PartialMethodTest();
+
+    public void Display()
+    {
+        PartialMethodTest();
+    }
+}
+
+partial class PartialClassTest
+{
+    partial void PartialMethodTest()
+    {
+        Console.WriteLine(str);
+    }
+}
+```
+上面这段代码示例了分部类和方法，执行```Display()```方法在下列选项中可以打印出的字符串是：
+
+## 答案
+
+```csharp
+Hello CSDN!
+```
+
+## 选项
+
+### A
+
+```csharp
+str
+```
+
+### B
+
+```csharp
+null
+```
+
+### C
+
+```csharp
+抛出异常
+```
\ No newline at end of file

data/1..NET初阶/3.C#特性/1.C#3.0特性/sample/Program.cs

@@ -63,5 +63,76 @@ public static class Extensions
 }
 
 // 隐式类型本地变量
+var i = “Hello CSDN！”;
+
 // 分部方法
-// 对象和集合初始值设定项
\ No newline at end of file
+partial class PartialClassTest
+{
+    readonly string str = "Hello CSDN!";
+
+    partial void PartialMethodTest();
+
+    public void Display()
+    {
+        PartialMethodTest();
+    }
+}
+
+partial class PartialClassTest
+{
+    partial void PartialMethodTest()
+    {
+        Console.WriteLine(str);
+    }
+}
+
+
+// 对象和集合初始值设定项
+public class Cat
+{
+    // 自动实现的属性
+    public int Age { get; set; }
+    public string Name { get; set; }
+
+    public Cat()
+    {
+    }
+
+    public Cat(string name)
+    {
+        this.Name = name;
+    }
+}
+
+Cat cat = new Cat { Age = 10, Name = "Fluffy" };
+Cat sameCat = new Cat("Fluffy"){ Age = 10 };
+
+var testA = new { name = "Gao", age = 996 };
+
+List<int> digits = new List<int> { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }; 
+
+public class MatrixTest
+{
+    private readonly double[,] storage = new double[3, 3];
+
+    public double this[int row, int column]
+    {
+        get { return storage[row, column]; }
+        set { storage[row, column] = value; }
+    }
+}
+
+var identity = new MatrixTest()
+{
+    [0, 0] = 1.0,
+    [0, 1] = 0.0,
+    [0, 2] = 0.0,
+
+    [1, 0] = 0.0,
+    [1, 1] = 1.0,
+    [1, 2] = 0.0,
+
+    [2, 0] = 0.0,
+    [2, 1] = 0.0,
+    [2, 2] = 1.0
+};
\ No newline at end of file