private void SetupDataReaderDeserializer(Type type, DbDataReader reader)
{
if (ReferenceEquals(type, returnType))
{
return;
}
var columnNames = DbQueryInternal.IsClrType(type) ? NoColumnNames : DbQueryInternal.GetColumnNames(reader);
var columnTypes = DbQueryInternal.GetColumnTypes(reader);
dataReaderDeserializer = DataReaderDeserializerCache.GetCachedOrBuildNew(connectionType, type, columnNames, columnTypes);
returnType = type;
}
private void SetupDataReaderDeserializer(DbDataReader reader)
{
if (returnType != null)
{
return;
}
var columnNames = DbQueryInternal.GetColumnNames(reader);
var columnTypes = DbQueryInternal.GetColumnTypes(reader);
returnType = DynamicTypeCache.GetCachedOrBuildNew(columnNames, columnTypes);
dataReaderDeserializer = DataReaderDeserializerCache.GetCachedOrBuildNew(connectionType, returnType, columnNames, columnTypes);
}
/// <summary>
/// Execute query and return the only element in the result, or a default element if the result is empty; this method throws an exception if there is not exactly one element in the result.
/// </summary>
/// <param name="connection">Database connection.</param>
/// <param name="parameters">Query parameters.</param>
/// <param name="transaction">Transaction to use.</param>
/// <returns>Single element in the result or the default value.</returns>
public dynamic QuerySingleOrDefault(IDbConnection connection, object parameters = null, IDbTransaction transaction = null)
{
if (connection == null)
{
ThrowException.ValueCannotBeNull(nameof(connection));
}
using (var command = SetupCommand(connection, parameters, transaction))
using (var reader = (DbDataReader)command.ExecuteReader(CommandBehavior.SingleResult | CommandBehavior.SequentialAccess))
{
SetupDataReaderDeserializer(reader);
return(DbQueryInternal.QuerySingleOrDefault <dynamic>(reader, dataReaderDeserializer));
}
}
