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nameof

ref:
https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/operators/nameof
https://www.huanlintalk.com/post/2015-01-28-csharp6-enhanced-expressions/

nameof 表示式

C# 6 (visual studio 2015) 新增的 nameof 關鍵字可用來取得某變數的名稱。請看底下這個簡單範例，便能了解其作用：

string firstName = "Joey";
string varName = nameof(firstName);  // 編譯結果：varName = "firstName"

常用如下
        public CItemMap(string sBuilding, int iFloorIndex)
        {
            if (string.IsNullOrEmpty(sBuilding))
                throw new ArgumentOutOfRangeException(nameof(sBuilding));
            if (iFloorIndex<0)
                throw new ArgumentOutOfRangeException(nameof(iFloorIndex));
            msBuilding = sBuilding;
            miFloorIndex = iFloorIndex;
        }

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Console.WriteLine(nameof(System.Collections.Generic));  // output: Generic
Console.WriteLine(nameof(List<int>));  // output: List
Console.WriteLine(nameof(List<int>.Count));  // output: Count
Console.WriteLine(nameof(List<int>.Add));  // output: Add

var numbers = new List<int> { 1, 2, 3 };
Console.WriteLine(nameof(numbers));  // output: numbers
Console.WriteLine(nameof(numbers.Count));  // output: Count
Console.WriteLine(nameof(numbers.Add));  // output: Add

As the preceding example shows, in the case of a type and a namespace, the produced name is not fully qualified.

In the case of verbatim identifiers, the @ character is not the part of a name, as the following example shows:

var @new = 5;
Console.WriteLine(nameof(@new));  // output: new


A nameof expression is evaluated at compile time and has no effect at run time.

You can use a nameof expression to make the argument-checking code more maintainable:

補充
            string s1 = nameof(CKeyType); // output: CKeyType  (class name)
            s1 = nameof(FCollection);     // output: FCollection (form name)
            s1 = nameof(FParent.MainMenuStrip); // output: MainMenuStrip (control name)