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- TheOracleConnectionis 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);
}
}
}
}
}