Trying to use an SPWeb object that has been closed or disposed and is no longer valid.

Question

I debugged this code and it never throws me an exception, however after ALL code is executed I got this message

Trying to use an SPWeb object that has been closed or disposed and is no longer valid.

protected void Button1_Click(object sender, EventArgs e)
        {
            CreateDestinationDocumentLibrary(TxtDocumentLibraryName.Text, TxtDestinationSiteUrl.Text);
            CopyFilesFromRoot(TxtDocumentLibraryName.Text, TxtDestinationSiteUrl.Text);
        }

        private void CreateDestinationDocumentLibrary(string documentLibraryname, string destinationSiteUrl)
        {
            using (SPSite oSPSite = SPContext.Current.Site)
            {
                using (SPWeb oSPWeb = oSPSite.OpenWeb(destinationSiteUrl))
                {
                    SPList newDocLibrary = oSPWeb.Lists.TryGetList(documentLibraryname);
                    if (newDocLibrary == null)
                    {
                        oSPWeb.Lists.Add(documentLibraryname, documentLibraryname, SPListTemplateType.DocumentLibrary);
                    }
                }
            }            
        }

        public void CopyFilesFromRoot(string documentLibraryname, string destinationSiteUrl)
        {
            using (SPSite oSPSite = SPContext.Current.Site)
            {
                using (SPWeb oSPWeb = oSPSite.RootWeb)
                {
                    SPFolder oFolder = oSPWeb.GetFolder(documentLibraryname);
                    SPFileCollection collFile = oFolder.Files;
                    //Copying files from the Root folder.
                    CopyFiles(destinationSiteUrl, documentLibraryname, collFile);
                    // Get the sub folder collection
                    SPFolderCollection collFolder = oFolder.SubFolders;
                    EnumerateFolders(destinationSiteUrl, documentLibraryname, collFolder);
                }
            }
        }

        public void CopyFiles(string destinationSiteUrl, string documentlibraryname, SPFileCollection collFile)
        {
            //SPFileCollection collFile = oFolder.Files;
            foreach (SPFile oFile in collFile)
            {
                oFile.CopyTo(destinationSiteUrl + "/" + documentlibraryname, true);
            }
        }

        private void EnumerateFolders(string destinationSiteUrl, string documentlibraryname, SPFolderCollection copyFolders)
        {
            foreach (SPFolder subFolder in copyFolders)
            {
                if (subFolder.Name != "Forms")
                {
                    SPFileCollection subFiles = subFolder.Files;
                    CopyFiles(destinationSiteUrl, documentlibraryname, subFiles);
                }
                SPFolderCollection subFolders = subFolder.SubFolders;
                EnumerateFolders(destinationSiteUrl, documentlibraryname, subFolders);
            }
        }

Answer 1

Never put SPContext.Current.Site (or web) into a variable in a using statement. You're not allowed to dispose them, they are passed on to the next web part and SharePoint will dispose them when done.

So change

using (SPSite oSPSite = SPContext.Current.Site) 
{ 
....
} 

to

SPSite oSPSite = SPContext.Current.Site;
....

Answer 2

In your "CreateDestinationDocumentLibrary" method, you wrap the SPSite object from context in a using statement. That forces the Dispose() method to be invoked.

You did not create that SPSite object, so you should not dispose of it. Never dispose of anything in SPContext.