Question

我正在尝试使用Dapper与现有数据库格式进行交互，该数据库格式的表格的持续时间编码为BIGINT列中的刻度。在插入和读取数据库时，如何告诉Dapper将我的POCO的TimeSpan - 类型属性映射到滴答？

我尝试将TimeSpan的类型地图设置为DbType.Int64：

SqlMapper.AddTypeMap(typeof(TimeSpan), DbType.Int64);

我还创建了ITypeHandler，但永远不会调用SetValue方法：

public class TimeSpanToTicksHandler : SqlMapper.TypeHandler<TimeSpan>
{
    public override TimeSpan Parse(object value)
    {
        return new TimeSpan((long)value);
    }

    public override void SetValue(IDbDataParameter parameter, TimeSpan value)
    {
        parameter.Value = value.Ticks;
    }
}

这是我的POCO：

public class Task
{
    public TimeSpan Duration { get; set; }

    // etc.
}

执行这样的简单插入语句时：

string sql = "INSERT INTO Tasks (Duration) values (@Duration);";

将POCO作为插入对象传递：

Task task = new Task { Duration = TimeSpan.FromSeconds(20) };
connection.Execute(sql, task);

我得到了这个例外：

System.InvalidCastException : Unable to cast object of type 'System.TimeSpan' to type 'System.IConvertible'.
   at System.Convert.ToInt64(Object value, IFormatProvider provider)
   at System.Data.SQLite.SQLiteStatement.BindParameter(Int32 index, SQLiteParameter param)
   at System.Data.SQLite.SQLiteStatement.BindParameters()
   at System.Data.SQLite.SQLiteCommand.BuildNextCommand()
   at System.Data.SQLite.SQLiteCommand.GetStatement(Int32 index)
   at System.Data.SQLite.SQLiteDataReader.NextResult()
   at System.Data.SQLite.SQLiteDataReader..ctor(SQLiteCommand cmd, CommandBehavior behave)
   at System.Data.SQLite.SQLiteCommand.ExecuteReader(CommandBehavior behavior)
   at System.Data.SQLite.SQLiteCommand.ExecuteNonQuery(CommandBehavior behavior)
   at System.Data.SQLite.SQLiteCommand.ExecuteNonQuery()
   at Dapper.SqlMapper.ExecuteCommand(IDbConnection cnn, ref CommandDefinition command, Action`2 paramReader) in SqlMapper.cs: line 3310
   at Dapper.SqlMapper.ExecuteImpl(IDbConnection cnn, ref CommandDefinition command) in SqlMapper.cs: line 1310
   at Dapper.SqlMapper.Execute(IDbConnection cnn, String sql, Object param, IDbTransaction transaction, Nullable`1 commandTimeout, Nullable`1 commandType) in SqlMapper.cs: line 1185

如果我按原样保留TimeSpan类型映射（默认为DbType.Time），则会写入TimeSpan的字符串版本，即“00：00：20.000”，这没有用，因为它与列中其他数据的格式不匹配。

Answer 1

你可以这样做吗？

public class Task
{
    public TimeSpan Duration { get; set; }
    public long Ticks 
    { 
        get { return Duration.Ticks; }
        set { Duration = new TimeSpan(value); }
    }
    // etc.
}

string sql = "INSERT INTO Tasks (Duration) values (@Ticks);";

Answer 2

LinqToDB的解决方案：

MappingSchema.SetDataType(typeof(TimeSpan), DataType.Int64);

或者：

    public class Program
{
    private const string ConnectionString = "Data Source=:memory:;Version=3;New=True;";

    public static void Main()
    {
        var dataProvider = new SQLiteDataProvider();

        var connection = dataProvider.CreateConnection(ConnectionString);
        connection.Open();

        var dataConnection = new DataConnection(dataProvider, connection);

        dataConnection.MappingSchema.SetDataType(typeof(TimeSpan), DataType.Int64);

        dataConnection.CreateTable<Category>();

        dataConnection.GetTable<Category>()
            .DataContextInfo
            .DataContext
            .Insert(new Category
            {
                Id = 2,
                Time = new TimeSpan(10, 0, 0)
            });


        foreach (var category in dataConnection.GetTable<Category>())
        {
            Console.WriteLine($@"Id: {category.Id}, Time: {category.Time}");
        }
    }

    private class Category
    {
        public int Id { get; set; }
        public TimeSpan Time { get; set; }
    }
}

示例：

{{1}}

在SQLite和Dapper中映射TimeSpan

2 个答案: