DllImport,如何检查DLL是否已加载？

using System.Runtime.InteropServices;

[DllImport("kernel32.dll")]
public static extern IntPtr GetModuleHandle(string lpModuleName);

public static bool IsDllLoaded(string dllName)
{
    return GetModuleHandle(dllName) != IntPtr.Zero;
}

using System.Runtime.InteropServices;

public static bool IsDllLoaded(string dllName)
{
    return LoadLibrary(dllName) != IntPtr.Zero;
}

[DllImport("kernel32.dll")]
public static extern IntPtr LoadLibrary(string dllToLoad);

[DllImport("kernel32.dll")]
public static extern IntPtr GetProcAddress(IntPtr hModule, string procedureName);