ReadAsync(byte[], int, int, CancellationToken)

This method returns a Task-based asynchronous version of OracleBFile.Read(), which reads a specified number of bytes from the OracleBFile instance and populates the buffer.

Declaration

// C#
public override Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)

Parameters

buffer - The byte array buffer to be populated.
offset - The starting offset (in bytes) at which the buffer is populated.
count - The number of bytes to read.
cancellationToken - The input cancellation token which can be used by the application to cancel the task.

Return Value

Task<Int> object representing the asynchronous operation immediately without blocking the calling thread for the whole duration of the query execution.

Implements

Stream

Exceptions

ObjectDisposedException - The object is already disposed.
InvalidOperationException - The OracleConnection is not open or has been closed during the lifetime of the object.
ArgumentOutOfRangeException - This exception is thrown if any of the following conditions exist:
- The offset or the count parameter is less than 0.
- The offset is greater than or equal to the buffer.Length.
- The offset and the count together are greater than the buffer.Length.

Example

using Oracle.ManagedDataAccess.Client;
using Oracle.ManagedDataAccess.Types;
using System;
using System.Threading;
using System.Threading.Tasks;

namespace AsyncApp
{
  class AsyncDemo
  {
    static async Task Main(string[] args)
    {
      string connectionString = "User Id=HR; Password=<PASSWORD>; Data Source=oracle;";

      OracleConnection oc = new OracleConnection(connectionString);
      await oc.OpenAsync(CancellationToken.None);

      OracleCommand cmd = oc.CreateCommand();
      cmd.CommandText = " select bfile_column from tab1";

      OracleDataReader reader = await cmd.ExecuteReaderAsync();

      await reader.ReadAsync(CancellationToken.None);
      using (var bfile = reader.GetOracleBFile(0))
      {
        bfile.OpenFile();
        byte[] buffer = new byte[100];

        //asynchronously read bfile data
        Task<int> task = bfile.ReadAsync(buffer, 0, 64, CancellationToken.None);

        //other operations
        Console.WriteLine("Hello World");

        //await for asynchronous ReadAsync 
        int bytesRead = await task;
        Console.WriteLine("Bytes Read: " + bytesRead);
      }
    }
  }
}