Dispose once only

MyDisposableObject.cs

private class MyDisposableObject : IDisposable, IAsyncDisposable
{
  private SqlConnection myResource = new SqlConnection();
  private bool isDisposed = false;

  public void Dispose()
  {
    if (!isDisposed)
    {
      isDisposed = true;
      myResource.Dispose();
    }
  }

  public async ValueTask DisposeAsync()
  {
    if (!isDisposed)
    {
      // Set isDisposed to true first
      isDisposed = true;
      await myResource.DisposeAsync();
    }
  }
}