Access denied to file in .Net

I am trying to copy an entire directory from one place to other through installer. Below is the mentioned Code

public static void copyDirectory(string Src, string Dst)
{
    String[] Files;

    if (Dst[Dst.Length - 1] != Path.DirectorySeparatorChar)
        Dst += Path.DirectorySeparatorChar;
    if (!Directory.Exists(Dst)) Directory.CreateDirectory(Dst);
    Files = Directory.GetFileSystemEntries(Src);
    foreach (string Element in Files)
    {
        // Sub direct开发者_如何学运维ories
        if (Directory.Exists(Element))
            copyDirectory(Element, Dst + Path.GetFileName(Element));
        // Files in directory
        else
            File.Copy(Element, Dst + Path.GetFileName(Element), true);

    }
}

It is giving me above error.please help me out in the above mentioned issue.

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1. make sure all applications that use that dll are closed.
2. since you are using "installer", but is still c# code, does it use the dll file?