How to use unsigned int / long types with Entity Framework?

entity-framework entity-framework-6 mysql

Question

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?

1
24
10/18/2014 3:25:18 AM

Accepted Answer

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.

42
9/9/2016 8:04:31 AM


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