/// <summary>
/// Iterates an IDataReader through the transform function and posts each record to the target block.
/// </summary>
/// <typeparam name="T">The return type of the transform function.</typeparam>
/// <param name="reader">The IDataReader to iterate.</param>
/// <param name="transform">The transform function for each IDataRecord.</param>
/// <param name="target">The target block to receivethe results.</param>
public static void ToTargetBlock <T>(this IDataReader reader,
ITargetBlock <T> target,
Func <IDataRecord, T> transform)
{
while (target.IsStillAlive() && reader.Read() && target.Post(transform(reader)))
{
}
}
/// <summary>
/// Asynchronously iterates an IDataReader and through the transform function and posts each record it to the target block.
/// </summary>
/// <typeparam name="T">The return type of the transform function.</typeparam>
/// <param name="command">The DbCommand to generate a reader from.</param>
/// <param name="target">The target block to receive the results.</param>
/// <param name="transform">The transform function for each IDataRecord.</param>
public static async Task ToTargetBlockAsync <T>(this DbCommand command,
ITargetBlock <T> target,
Func <IDataRecord, T> transform)
{
if (target.IsStillAlive())
{
if (command.Connection.State != ConnectionState.Open)
{
await command.Connection.EnsureOpenAsync();
}
using (var reader = await command.ExecuteReaderAsync())
{
if (target.IsStillAlive())
{
await reader.ToTargetBlockAsync(target, transform);
}
}
}
}
/// <summary>
/// Asynchronously iterates an IDataReader and through the transform function and posts each record it to the target block.
/// </summary>
/// <typeparam name="T">The return type of the transform function.</typeparam>
/// <param name="reader">The SqlDataReader to read from.</param>
/// <param name="target">The target block to receive the results.</param>
/// <param name="transform">The transform function to process each IDataRecord.</param>
public static async Task ToTargetBlockAsync <T>(this DbDataReader reader,
ITargetBlock <T> target,
Func <IDataRecord, T> transform)
{
Task <bool> lastSend = null;
while (target.IsStillAlive() &&
await reader.ReadAsync() &&
(lastSend == null || await lastSend))
{
// Allows for a premtive read before waiting for the next send.
lastSend = target.SendAsync(transform(reader));
}
}