Creating a byte array from a stream

It really depends on whether or not you can trust s.Length. For many streams, you just don't know how much data there will be. In such cases - and before .NET 4 - I'd use code like this:

public static byte[] ReadFully(Stream input)
{
    byte[] buffer = new byte[16*1024];
    using (MemoryStream ms = new MemoryStream())
    {
        int read;
        while ((read = input.Read(buffer, 0, buffer.Length)) > 0)
        {
            ms.Write(buffer, 0, read);
        }
        return ms.ToArray();
    }
}

With .NET 4 and above, I'd use Stream.CopyTo, which is basically equivalent to the loop in my code - create the MemoryStream, call stream.CopyTo(ms) and then return ms.ToArray(). Job done.

I should perhaps explain why my answer is longer than the others. Stream.Read doesn't guarantee that it will read everything it's asked for. If you're reading from a network stream, for example, it may read one packet's worth and then return, even if there will be more data soon. BinaryReader.Read will keep going until the end of the stream or your specified size, but you still have to know the size to start with.

The above method will keep reading (and copying into a MemoryStream) until it runs out of data. It then asks the MemoryStream to return a copy of the data in an array. If you know the size to start with - or think you know the size, without being sure - you can construct the MemoryStream to be that size to start with. Likewise you can put a check at the end, and if the length of the stream is the same size as the buffer (returned by MemoryStream.GetBuffer) then you can just return the buffer. So the above code isn't quite optimised, but will at least be correct. It doesn't assume any responsibility for closing the stream - the caller should do that.

See this article for more info (and an alternative implementation).

MemoryStream ms = new MemoryStream();
file.PostedFile.InputStream.CopyTo(ms);
var byts = ms.ToArray();
ms.Dispose();

You can simply use ToArray() method of MemoryStream class, for ex-

MemoryStream ms = (MemoryStream)dataInStream;
byte[] imageBytes = ms.ToArray();

In case anyone likes it, here is a .NET 4+ only solution formed as an extension method without the needless Dispose call on the MemoryStream. This is a hopelessly trivial optimization, but it is worth noting that failing to Dispose a MemoryStream is not a real failure.

public static class StreamHelpers
{
    public static byte[] ReadFully(this Stream input)
    {
        var ms = new MemoryStream();
        input.CopyTo(ms);
        return ms.ToArray();
    }
}

Create a helper class and reference it anywhere you wish to use it.

public static class StreamHelpers
{
    public static byte[] ReadFully(this Stream input)
    {
        using (MemoryStream ms = new MemoryStream())
        {
            input.CopyTo(ms);
            return ms.ToArray();
        }
    }
}

In namespace RestSharp.Extensions there is method ReadAsBytes. Inside this method is used MemoryStream and there is the same code like in some examples on this page but when you are using RestSharp this is easiest way.

using RestSharp.Extensions;
var byteArray = inputStream.ReadAsBytes();

This is the function which I am using, tested and worked well. please bear in mind that 'input' should not be null and 'input.position' should reset to '0' before reading otherwise it will break the read loop and nothing will read to convert to array.

    public static byte[] StreamToByteArray(Stream input)
    {
        if (input == null)
            return null;
        byte[] buffer = new byte[16 * 1024];
        input.Position = 0;
        using (MemoryStream ms = new MemoryStream())
        {
            int read;
            while ((read = input.Read(buffer, 0, buffer.Length)) > 0)
            {
                ms.Write(buffer, 0, read);
            }
            byte[] temp = ms.ToArray();

            return temp;
        }
    }

If a stream supports the Length property, a byte array can be directly created. The advantage is that MemoryStream.ToArray creates the array twice. Plus, probably some unused extra bytes in the buffer. This solution allocates the exact array needed. If the stream does not support the Length property, it will throw NotSupportedException exception.

It is also worth noting that arrays cannot be bigger than int.MaxValue.

public static async Task<byte[]> ToArrayAsync(this Stream stream)
{
    var array = new byte[stream.Length];
    await stream.ReadAsync(array, 0, (int)stream.Length);
    return array;
}

Complete code which switches between both versions based on whether the stream supports seeking or not.

/// <summary>
/// Converts stream to byte array.
/// </summary>
/// <param name="stream">Stream</param>
/// <returns>Binary data from stream in an array</returns>
public static async Task<byte[]> ToArrayAsync(this Stream stream)
{
    if (!stream.CanRead)
    {
        throw new AccessViolationException("Stream cannot be read");
    }

    if (stream.CanSeek)
    {
        return await ToArrayAsyncDirect(stream);
    }
    else
    {
        return await ToArrayAsyncGeneral(stream);
    }
}

private static async Task<byte[]> ToArrayAsyncGeneral(Stream stream)
{
    using (var memoryStream = new MemoryStream())
    {
        await stream.CopyToAsync(memoryStream);
        return memoryStream.ToArray();
    }
}

private static async Task<byte[]> ToArrayAsyncDirect(Stream stream)
{
    var array = new byte[stream.Length];
    await stream.ReadAsync(array, 0, (int)stream.Length);
    return array;
}

Since there's no modern (i.e. async) version of this answer, this is the extension method I use for this purpose:

public static async Task<byte[]> ReadAsByteArrayAsync(this Stream source)
{
    // Optimization
    if (source is MemoryStream memorySource)
        return memorySource.ToArray();

    using var memoryStream = new MemoryStream();
    await source.CopyToAsync(memoryStream);
    return memoryStream.ToArray();
}

The optimization is based on the fact the source code for ToArray calls some internal methods.