Merge Files using C#

public static void Merge(string inputfile, string inputpath, string outputpath, string exten)
{
    //string outPath = inputpath;
    string[] tmpFiles = Directory.GetFiles(inputpath, inputfile + "*" + exten);
    FileStream outputFile = new FileStream(outputpath, FileMode.OpenOrCreate, FileAccess.Write);
    string prevFileName = "";
    foreach (string tempFile in tmpFiles)
    {
        string fileName = Path.GetFileNameWithoutExtension(tempFile);
        string baseFileName = fileName;
        string extension = Path.GetExtension(fileName);
        int bytesRead = 0;
        byte[] buffer = new byte[1024];
        FileStream inputTempFile = new FileStream(tempFile, FileMode.OpenOrCreate, FileAccess.Read);
        while ((bytesRead = inputTempFile.Read(buffer, 0, 1024)) > 0)
        outputFile.Write(buffer, 0, bytesRead);
        inputTempFile.Close();
        prevFileName = baseFileName;
    }
    outputFile.Close();
}