In C# you can flag a value type as a nullable type by adding ? after the type (like int? x;).

在C#中，你可以在一个允许为空的值类型后面加上一个问号（比如，int? x;）。

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Methods 31 cases of thoracolumbar fracture and dislocation have been studied during surgically hyperextensive reduction with multipurpose surgical table and C type X ray machine.

方法用多功能手术台、C形臂X线机对31例胸腰段骨折脱位患者进行术中过伸复位研究。

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