how to convert byte array RGB image without BMP header to bitmap using c#

Since you have no header information, you have to know the dimensions of your source bitmap and create a matching bitmap, then you lock the bits and copy the raw bytes according to the format of your input image. The following snippet should get you on the way:
The sourceBitmap "class" is a meta-container, you have to obtain your information from your source knowledge.

Bitmap myBitmap = new Bitmap(sourceBitmap.Width, sourceBitmap.Height, PixelFormat.Format24bppRgb);

BitmapData myData = myBitmap.LockBits(sourceBitmap.Dimensions, ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);

int sStride = sourceBitmap.Stride;
int dStride = myData.Stride;

// copy the RGB bits from your raw source bitmap to the buffer of 
// myBitmap, myData.Scan0 is the first byte of the target buffer.
unsafe
{
  byte* src = <your pointer="" to="" the="" raw="" data="">;
  byte* dst = (byte*)myData.Scan0.ToPointer();
  byte* s;
  byte* d;
  for(int row = 0; row < sourceBitmap.Height; row++)
  {
    for(int col = 0; col < sourceBitmap.Width; col++)
    {
       s = src + row * sStride + col * 3; //24bpp, 3 bytes per pixel
       d = dst + row * dStride + col * 3; //24bpp, 3 bytes per pixel
       d[0] = s[0];
       d[1] = s[1];
       d[2] = s[2];
    }
  }
}

myBitmap.UnlockBits(myData);
</your>

Now you can display the image using myBitmap.