asp.net – 从数据库加载时,DateTime.Kind设置为未指定,而不是UT

已经提出了类似的问题,并且答案倾向于暗示进入ObjectContext.ObjectMaterialized事件,但是对于使用投影的查询,它没有触发.

我将提出的解决方案适用于实体和投影查询,方法是在DbDataReader级别执行转换(由此类查询使用).

为此,我们需要一个拦截GetDateTime方法的自定义DbDataReader实现.不幸的是,实现DbDataReader派生类需要很多样板代码.幸运的是,我已经创建了一个基类形式,我对Dynamic Translate to avoid C# syntax errors的回答只是将每个方法委托给底层的DbDataReader实例,所以我只是从那里拿它：

abstract class DelegatingDbDataReader : DbDataReader
{
    readonly DbDataReader source;
    public DelegatingDbDataReader(DbDataReader source)
    {
        this.source = source;
    }
    public override object this[string name] { get { return source[name]; } }
    public override object this[int ordinal] { get { return source[ordinal]; } }
    public override int Depth { get { return source.Depth; } }
    public override int FieldCount { get { return source.FieldCount; } }
    public override bool HasRows { get { return source.HasRows; } }
    public override bool IsClosed { get { return source.IsClosed; } }
    public override int RecordsAffected { get { return source.RecordsAffected; } }
    public override bool GetBoolean(int ordinal) { return source.GetBoolean(ordinal); }
    public override byte GetByte(int ordinal) { return source.GetByte(ordinal); }
    public override long GetBytes(int ordinal,long dataOffset,byte[] buffer,int bufferOffset,int length) { return source.GetBytes(ordinal,dataOffset,buffer,bufferOffset,length); }
    public override char GetChar(int ordinal) { return source.GetChar(ordinal); }
    public override long GetChars(int ordinal,char[] buffer,int length) { return source.GetChars(ordinal,length); }
    public override string GetDataTypeName(int ordinal) { return source.GetDataTypeName(ordinal); }
    public override DateTime GetDateTime(int ordinal) { return source.GetDateTime(ordinal); }
    public override decimal GetDecimal(int ordinal) { return source.GetDecimal(ordinal); }
    public override double GetDouble(int ordinal) { return source.GetDouble(ordinal); }
    public override IEnumerator GetEnumerator() { return source.GetEnumerator(); }
    public override Type GetFieldType(int ordinal) { return source.GetFieldType(ordinal); }
    public override float GetFloat(int ordinal) { return source.GetFloat(ordinal); }
    public override Guid GetGuid(int ordinal) { return source.GetGuid(ordinal); }
    public override short GetInt16(int ordinal) { return source.GetInt16(ordinal); }
    public override int GetInt32(int ordinal) { return source.GetInt32(ordinal); }
    public override long GetInt64(int ordinal) { return source.GetInt64(ordinal); }
    public override string GetName(int ordinal) { return source.GetName(ordinal); }
    public override int GetOrdinal(string name) { return source.GetOrdinal(name); }
    public override string GetString(int ordinal) { return source.GetString(ordinal); }
    public override object GetValue(int ordinal) { return source.GetValue(ordinal); }
    public override int GetValues(object[] values) { return source.GetValues(values); }
    public override bool IsDBNull(int ordinal) { return source.IsDBNull(ordinal); }
    public override bool NextResult() { return source.NextResult(); }
    public override bool Read() { return source.Read(); }
    public override void Close() { source.Close(); }
    public override T GetFieldValue<T>(int ordinal) { return source.GetFieldValue<T>(ordinal); }
    public override Task<T> GetFieldValueAsync<T>(int ordinal,CancellationToken cancellationToken) { return source.GetFieldValueAsync<T>(ordinal,cancellationToken); }
    public override Type GetProviderSpecificFieldType(int ordinal) { return source.GetProviderSpecificFieldType(ordinal); }
    public override object GetProviderSpecificValue(int ordinal) { return source.GetProviderSpecificValue(ordinal); }
    public override int GetProviderSpecificValues(object[] values) { return source.GetProviderSpecificValues(values); }
    public override DataTable GetSchemaTable() { return source.GetSchemaTable(); }
    public override Stream GetStream(int ordinal) { return source.GetStream(ordinal); }
    public override TextReader GetTextReader(int ordinal) { return source.GetTextReader(ordinal); }
    public override Task<bool> IsDBNullAsync(int ordinal,CancellationToken cancellationToken) { return source.IsDBNullAsync(ordinal,cancellationToken); }
    public override Task<bool> ReadAsync(CancellationToken cancellationToken) { return source.ReadAsync(cancellationToken); }
    public override int VisibleFieldCount { get { return source.VisibleFieldCount; } }
}

并构建我们需要的实际类：

class UtcDateTimeConvertingDbDataReader : DelegatingDbDataReader
{
    public UtcDateTimeConvertingDbDataReader(DbDataReader source) : base(source) { }
    public override DateTime GetDateTime(int ordinal)
    {
        return DateTime.SpecifyKind(base.GetDateTime(ordinal),DateTimeKind.Utc);
    }
}

一旦我们有了这个,我们需要使用EF interception将其插入EF基础设施.

我们首先创建一个自定义DbCommandInterceptor派生类：

class UtcDateTimeConvertingDbCommandInterceptor : DbCommandInterceptor
{
    public override void ReaderExecuted(DbCommand command,DbCommandInterceptionContext<DbDataReader> interceptionContext)
    {
        base.ReaderExecuted(command,interceptionContext);
        if (interceptionContext.Result != null && interceptionContext.Exception == null)
            interceptionContext.Result = new UtcDateTimeConvertingDbDataReader(interceptionContext.Result);
    }
}

注册它(例如从你的DbContext派生类静态构造函数)：

public class YourDbContext : DbContext
{
    static YourDbContext()
    {
        DbInterception.Add(new UtcDateTimeConvertingDbCommandInterceptor());
    }
    // ...
}

我们完成了.

现在,来自数据库的每个DateTime值都将Kind属性设置为Utc.