1.忽略转义字符
例如
string fileName = "D:\\文本文件\\text.txt";
使用@后
string fileName = @"D:\文本文件\text.txt";

2.让字符串跨行
例如
string strSQL = "SELECT * FROM HumanResources.Employee AS e"
    " INNER JOIN Person.Contact AS c"
    " ON e.ContactID = c.ContactID"
    " ORDER BY c.LastName";
使用@后
string strSQL = @"SELECT * FROM HumanResources.Employee AS e
    INNER JOIN Person.Contact AS c
    ON e.ContactID = c.ContactID
    ORDER BY c.LastName";

3.在标识符中的用法 【虽然可以，但强烈建议不这样使用】
C#是不允许关键字作为标识符(类名、变量名、方法名、表空间名等)使用的，但如果加上@之后就可以了
例如
public static void @static(int @int)
        {
            if (@int > 0)
            {
                System.Console.WriteLine("Positive Integer");
            }
            else if (@int == 0)
            {
                System.Console.WriteLine("Zero");
            }
            else
            {
                System.Console.WriteLine("Negative Integer");
            }
        }