/// <summary>
/// Executes an INSERT, UPDATE, or DELETE statement.
/// </summary>
/// <param name="sql">The SQL to execute</param>
/// <returns>
/// The number of rows affected by the statement
/// </returns>
internal int ExecuteNonQuery(string sql)
{
using (IDbCommandFactory c = GetCommandFactory())
using (IDbCommand cmd = c.GetCommand(sql))
{
return(cmd.ExecuteNonQuery());
}
}
/// <summary>
/// Executes a query
/// </summary>
/// <typeparam name="T">The type of data produced by the query.</typeparam>
/// <param name="query">The query to be executed</param>
/// <returns>The rows (if any) that satisfy the query</returns>
/// <seealso cref="ExecuteSelect"/>
internal IEnumerable <T> ExecuteQuery <T>(IDataQuery <T> query)
{
using (IDbCommandFactory c = GetCommandFactory())
using (IDbCommand cmd = c.GetCommand(query.Text))
using (IDataReader reader = cmd.ExecuteReader())
{
while (reader.Read())
{
yield return(query.CreateInstance(reader));
}
}
}
/// <summary>
/// Executes a query that is expected to return no more than one row.
/// </summary>
/// <typeparam name="T">The type of data in the query field.</typeparam>
/// <param name="sql">The query text</param>
/// <param name="defaultValue">The default value to be returned in cases
/// where nothing was found, or a database null was found.</param>
/// <returns>The selected value (or <paramref name="defaultValue"/> if not found)</returns>
/// <remarks>There is no error if the select actually relates to multiple rows
/// (in that case, you just get the first row that was selected).</remarks>
/// <seealso cref="ExecuteQuery"/>
internal T ExecuteSelect <T>(string sql, T defaultValue = default(T)) where T : IConvertible
{
using (IDbCommandFactory c = GetCommandFactory())
using (IDbCommand cmd = c.GetCommand(sql))
{
object o = cmd.ExecuteScalar();
if (o == null || o == DBNull.Value)
{
return(defaultValue);
}
return((T)Convert.ChangeType(o, typeof(T)));
}
}
