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

The ReadAsync method returns a Task-based asynchronous version of OracleBlob.Read(), which reads a specified number of bytes from the ODP.NET LOB 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.

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 blob_column from tab1";


      OracleDataReader reader = await cmd.ExecuteReaderAsync();

      while (await reader.ReadAsync(CancellationToken.None))
      {
        using (OracleBlob blob = reader.GetOracleBlob(0))
        {
          byte[] buffer = new byte[100];
          //asynchronously read blob data
          Task<int> task = blob.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);
        }
      }
    }
  }
}