Prevent duplicate values in SharePoint 2007 list column

In SharePoint 2007 list, if we want to prevent duplicate values in a column, we can make use of the SPServices MakeUnque function.

More details are here:
http://spservices.codeplex.com/wikipage?title=$%28%29.SPServices.SPRequireUnique&referringTitle=Documentation

Currently, the function works only with Single line of textcolumns.

Cannot perform this operation. The file is no longer checked out or has been deleted - SharePoint Designer 2013

While working in SharePoint Designer 2013, sometime it demanded to check out files that are not checked in, refused to check in other files. And it shows below error message:

Cannot perform this operation. The file is no longer checked out or has been deleted

After some search on google, I found this post, which helped a lot.

We need to clear the cache of sharepoint designer. The cache is composed of these 2 folders:

• %APPDATA%\Microsoft\Web Server Extensions\Cache
• %USERPROFILE%\AppData\Local\Microsoft\WebsiteCache

Just delete their contents and you are done.

External Content Type to read data from SQL Server using SQL Authentication

Found below a good artical on creating external list to read data from SQL server using SQL Authentication:
http://blogs.msdn.com/b/mvpawardprogram/archive/2012/04/12/sharepoint-2010-external-content-type-to-read-data-from-sql-server-using-sql-authentication-and-secure-store-service.aspx

How to add external css in visual webpart in SharePoint 2010

If you want to add external css on visual webpart,

1. First go to layouts folder in 14 hive, path is C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\LAYOUTS
2. Create a new folder in it and give a proper name to that folder.
3. Add your css files in that newly created folder.
4. Now to call the css file from your webpart code, add below tag in your ascx file <SharePoint:CssRegistration ID="cssReg" runat="server" Name="/_layouts/ForCss/style.css"></SharePoint:CssRegistration>

Done. Hope this helps.