我想在 EF-Core 中创建 sqlite 函数，特别是 newid()，并使用 DbContext 使用现有的与 SQLServer 兼容的 c# 代码来使用它们。
当我创建一个实体时，newid() 函数在 dbcontext.SaveChanges() 之后被 EF-Core 调用。
我能够使用新的 SQLiteConnection 创建函数
var connection = new SQLiteConnection(connectionString);
connection.CreateFunction("newid", () => Guid.NewGuid());
但是这些既不会持久化也不会被 DbContext 调用。
[DbFunction] 属性看起来很有前途，但我无法让它与 SQLite 数据库一起使用。
【问题讨论】：
标签： c# sqlite entity-framework-core
1. Add the [DbFunction] attribute to your function signature, specifying the function name and the schema name:
[DbFunction("newid", "dbo")]
public static Guid NewId()
{
return Guid.NewGuid();
}
2. In your DbContext, register the function using the modelBuilder:
modelBuilder.HasDbFunction(typeof(MyFunctions).GetMethod(nameof(MyFunctions.NewId)));
3. Use the function in your LINQ query, just like any other SQL function:
var data = dbContext.MyEntities
.Select(e => new {
Id = e.Id,
Guid = MyFunctions.NewId()
});
4. If you want the function to be called automatically by EF-Core when you call SaveChanges(), you can create a trigger in your SQLite database to call the function:
CREATE TRIGGER newid_trigger
AFTER INSERT ON MyEntities
BEGIN
UPDATE MyEntities
SET Guid = newid()
WHERE rowid = new.rowid;
END;
This approach allows you to use existing SQLServer code and consume SQLite functions in your DbContext, without having to create a new SQLiteConnection.
【讨论】：