internal async Task <object> ExecuteScalarHelperAsync(SqlCommand cmd)
{
DoPreExecute(cmd);
object r = await cmd.ExecuteScalarAsync().ConfigureAwait(false);
OnExecutedCommand(cmd);
return(r);
}
protected async Task<object> ExecuteScalarAsync(DbCommand command)
{
bool doClose = await InitializeConnectionAsync();
initializeCommand(ref command);
object ret = await command.ExecuteScalarAsync();
if (doClose)
Connection.Close();
return ret;
}
/// <summary>
/// 异步执行Command返回单值
/// </summary>
/// <param name="command">Command实例</param>
/// <returns>单值</returns>
private async Task<object> DoExecuteScalarAsync(DbCommand command)
{
ExceptionHelper.TrueThrow<ArgumentException>(command.CommandType == CommandType.TableDirect,
Resource.ExecuteScalarNotSupportTableDirectException);
using (DbContext context = await DbContext.GetContextAsync(this.name))
{
command.Connection = context.Connection;
DoDbEvent(command, DbEventType.BeforeExecution);
object returnValue = await command.ExecuteScalarAsync();
if (command.CommandType != CommandType.Text)
{
// 由于 SQL Server 在Stored Procedure和Function返回值处理方式上存在不同，因此增加了适应性修改
returnValue = (returnValue == null) ? command.Parameters[DefaultReturnValueParameterName].Value : returnValue;
}
DoDbEvent(command, DbEventType.AfterExecution);
return returnValue;
}
}