1 string a1 = null;　　// 僅僅是一個聲明，記憶體中並沒有分配用來存儲值的空間。
 2 
 3 string a1 = String.Empty;　　// 等價於 ""，以新建字元串長度為零的 String 對象，可以減少 NullReferenceException 發生的可能性。
 4 
 5 System.String greeting = "Hello World!";　　// 在記憶體中分配了一個連續性的不可變的儲存空間。
 6 
 7 // 長字元串字面量拆分為較短的字元串，從而提高源程式碼的可讀性。
 8 // 以下程式碼將較短的字元串連接起來，以創建長字元串字面量。 在編譯時將這些部分連接成一個字元串。 無論涉及到多少個字元串，均不產生運行時性能開銷。
 9 string text = "Historically, the world of data and the world of objects " +
10 "have not been well integrated. Programmers work in C# or Visual Basic " +
11 "and also in SQL or XQuery. On the one side are concepts such as classes, " +
12 "objects, fields, inheritance, and .NET Framework APIs. On the other side " +
13 "are tables, columns, rows, nodes, and separate languages for dealing with " +
14 "them. Data types often require translation between the two worlds; there are " +
15 "different standard functions. Because the object world has no notion of query, a " +
16 "query can only be represented as a string without compile-time type checking or " +
17 "IntelliSense support in the IDE. Transferring data from SQL tables or XML trees to " +
18 "objects in memory is often tedious and error-prone.";

 1 // 初始化 s1
 2 // 記憶體為 s1 分配了存放字元的空間
 3 string s1 = "A string is more ";
 4 
 5 // 初始化 s2
 6 // 記憶體為 s2 分配了存放字元的空間
 7 string s2 = "than the sum of its chars.";
 8 
 9 // 記憶體為 s1 重新分配了新值的空間
10 // 並指向新空間的地址，所以 s1 有了新的值
11 // 無用的s1舊值等待GC垃圾回收
12 s1 += s2;
13 
14 System.Console.WriteLine(s1);

StringBuilder strb = new StringBuilder();
strb.Append('*', 10).Append(" Adding Text to a StringBuilder Object ").Append('*', 10);
strb.AppendLine("\n");
strb.AppendLine("Some code points and their corresponding characters:");
for (int ctr = 50; ctr <= 60; ctr++) {
    strb.AppendFormat("{0,12:X4} {1,12}", ctr,Convert.ToChar(ctr));
    strb.AppendLine();
}