如何使用Entity Framework使用unsigned int / long类型？ [英] How to use unsigned int / long types with Entity Framework?

问题描述

当添加新的迁移（代码优先）但 ulong long 数据类型的类属性已正确映射c>数据类型被mysql的EF提供程序跳过。如何映射一个属性来使用mysql的 unsigned bigint ？

解决方案

事实证明，实体框架不支持 unsigned 数据类型。对于 uint 列，可以将值存储在范围较大的签名数据类型（即 long ）。 ulong 列？常见的解决方案对我来说无法工作，因为没有EF支持的签名数据类型可以持有 ulong 而不会溢出。

经过一番思考，我想出了一个简单的解决方案：只需将数据存储在支持的 long 类型中，并将其转换为 ulong 。你可能会想：但等等，ulong的最大值> long的最大值！您仍然可以将ulong的字节存储在一个很长的位置，然后在需要时将其重新设置为ulong，因为它们都有8个字节。这将允许您通过EF将一个ulong变量保存到数据库。

  //避免直接修改以下内容。 
 //仅用作数据库列。 
 public long __MyVariable {get;组; } 
 
 //访问/修改此变量。 
 //告诉EF不要将此字段映射到Db表
 [NotMapped] 
 public ulong MyVariable 
 {
 get 
 {
未选中
 {
 return（ulong）__ MyVariable; 
} 
} 
 
 set 
 {
 unchecked 
 {
 __MyVariable =（long）value; 
} 
} 
} 
  

投票是 unchecked 以防止溢出异常。

希望这有助于某人。

Class properties with the long data type are properly mapped when adding a new migration (code-first), but ulong data types are skipped by mysql's EF provider. How does one map a property to use mysql's unsigned bigint?

解决方案

Turns out that Entity Framework does not support unsigned data types. For uint columns, one could just store the value in a signed data type with a larger range (that is, a long). What about ulong columns? The common solution couldn't work for me because there is no EF-supported signed data type that can hold a ulong without overflowing.

After a bit of thinking, I figured out a simple solution to this problem: just store the data in the supported long type and cast it to ulong when accessed. You might be thinking: "But wait, ulong's max value > long's max value!" You can still store the bytes of a ulong in a long and then cast it back to ulong when you need it, since both have 8 bytes. This will allow you to save a ulong variable to a database through EF.

// Avoid modifying the following directly.
// Used as a database column only.
public long __MyVariable { get; set; }

// Access/modify this variable instead.
// Tell EF not to map this field to a Db table
[NotMapped]
public ulong MyVariable
{
    get
    {
        unchecked
        {
            return (ulong)__MyVariable;
        }
    }

    set
    {
        unchecked
        {
            __MyVariable = (long)value;
        }
    }
}

The casting is unchecked to prevent overflow exceptions.

Hope this helps someone.

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