/// <summary>
/// Gets the first value of the first table of the first row.
/// </summary>
/// <param name="records">The source sequence to get the value from.</param>
/// <returns>The value converted to the specified type.</returns>
/// <remarks>Additional rows, tables and columns are ignored.</remarks>
/// <exception cref="InvalidOperationException">Thrown if there is not at least one value to read from the supplied records.</exception>
public static object GetScalar(this IEnumerable <Record> records)
{
if (records == null)
{
throw new ArgumentNullException(nameof(records));
}
// Get the single row
Record row = records.FirstOrDefault();
if (row == null)
{
throw new InvalidOperationException($"To get a scalar value the {nameof(Record)} sequence must contain at least one row.");
}
// Get the single table
RecordItem item = row.Values.FirstOrDefault();
if (item == null)
{
throw new InvalidOperationException($"To get a scalar value the {nameof(Record)} sequence must contain at least one table on its first row.");
}
// Check there is a column to read from
if (item.Count == 0)
{
throw new InvalidOperationException($"To get a scalar value the {nameof(Record)} sequence must contain at least one column on the first table on its first row.");
}
// Get the value from the item
return(item.Values.FirstOrDefault());
}
private static RecordItem ReadItem(this DbDataReader reader, IEnumerable <CommandField> fields, string type)
{
RecordItem item = new RecordItem(type);
foreach (CommandField field in fields)
{
object value = reader[field.Ordinal];
if (value is DBNull)
{
value = null;
}
item[field.FieldName] = value;
}
return(item);
}
