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1.使用场景 2.参考文章及示例代码下载
msdn:It returns the left-hand operand if it is not null; otherwise it returns the right operand.如果左侧值不为空的话,返回左侧的值,否则返回右面的值,下面是一个测试示例:
class NullCoalesce { static int? GetNullableInt() { return null; } static string GetStringValue() { return null; } static void Main() { // ?? operator example. int? x = null; // y = x, unless x is null, in which case y = -1. int y = x ?? -1; // Assign i to return value of method, unless // return value is null, in which case assign // default value of int to i. int i = GetNullableInt() ?? default(int); string s = GetStringValue(); // ?? also works with reference types. // Display contents of s, unless s is null, // in which case display "Unspecified". Console.WriteLine(s ?? "Unspecified"); } }
2.参考文章及示例代码下载参考文章: http://msdn.microsoft.com/en-us/library/ms173224.aspx |
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