How to check whether a List is a Document Library?

Many times, we face a situation where we iterate through list collection. Now if we need to check whether a list is a SPDocumentLibrary or not, we can check it in very simple manner:

Suppose we need to display list of document libraries present in a site in a dropdown control named 'lstTargetLibrary', we will iterate through list collection and check for List type:


SPWeb site = SPContext.Current.Web;
foreach (SPList list in site.Lists) {
if (list is SPDocumentLibrary && !list.Hidden) {
SPDocumentLibrary docLib = (SPDocumentLibrary)list;

lstTargetLibrary.Items.Add(
new ListItem(docLib.Title, docLib.ID.ToString()));
}
}

How to Upload a File to a SharePoint Site from a Local Folder

This code sample will show how to upload a file from your local pc to Sharepoint site using object mode:

1. Create a project and import namespaces :

using System.IO;
using Microsoft.SharePoint;

2. The UploadFile funtion code:

public void UploadFile(string srcUrl, string destUrl)
{
if (! File.Exists(srcUrl))
{
throw new ArgumentException(String.Format("{0} does not exist",
srcUrl), "srcUrl");
}

SPWeb site = new SPSite(destUrl).OpenWeb();

FileStream fStream = File.OpenRead(srcUrl);
byte[] contents = new byte[fStream.Length];
fStream.Read(contents, 0, (int)fStream.Length);
fStream.Close();

EnsureParentFolder(site, destUrl);
site.Files.Add(destUrl, contents);
}

The UploadFile method accepts two parameters. The srcUrl parameter specifies the path of the source location in the file system of the local computer, and the destUrl parameter specifies the absolute URL of the destination. A System.IO.FileStream object is used to read the source file into a byte array for use with the Add method of the SPFileCollection class.

To upload a file from a local folder on the same server that is running Windows SharePoint Services, you can use a System.IO.FileStream object instead. In this case, add a using directive for the System.IO namespace, in addition to directives for System and Microsoft.SharePoint. The following example uses the Click event handler to call an UploadFile method, which in turn calls the previously described EnsureParentFolder method.

How to delete a List from Sharepoint ?

This small code snippets will demonstrate how to delete a SPList from a sharepoint site.

To delete a list, you must specify the GUID of the list as the parameter for the Delete method. Use the ID property of the SPList class to find the GUID.

SPWeb mySite = SPContext.Current.Web;
SPListCollection lists = mySite.Lists;

SPList list = lists[ListName];
System.Guid listGuid = list.ID;

lists.Delete(listGuid);

Difference between Update and SystemUpdate in Sharepoint

We all know that whenever we add a list item or do some modification, we update the list. Here we have two options:

1. List.Update() and 2. List.SystemUpdate()

The main difference betwwen two is that,

List.Update() creates automatically new version of list item as Update method is called.


List.SystemUpdate() avoids SharePoint 2007 to change modified date and modifier fields. Argument false tells that no new versions are expected.

SystemUpdate takes an boolean argument that set whether new version need to be created or not.

Example using SystemUpdate() :

SPList list = web.Lists["myList"];
SPListItem item = list.Items[0];
item["myField"] = "my value";

item.SystemUpdate(false);
list.Update();

UseFul Blog

http://lamahashim.blogspot.com/

Sharepoint videos links

http://blah.winsmarts.com/Books_Reviewed.aspx

http://dotnetdreamer.com/2009/05/24/creating-sites-using-sharepoint-object-model/

http://blah.winsmarts.com/Sharepoint.aspx

Handling AccessDenied Exception to implement our logic

The SPUtility.HandleAccessDenied method provides the functionality to redirect users to the standard "Access Denied Page" pragmatically, thus asking them to re-logon. One of the scenarios of such usage is the public sites, where access to the standard SharePoint specific pages still exists and you want to block those pages

However, you can handle access denied exception via SPSecurity.CatchAccessDeniedException = true

Access deined exception is handled by sharepoint platform and user will be redirected to _layouts/AccessDenied.aspx page if user doesnt have permission to perform that task. This might casue usability problem in some cases. You can handle access denied exception in your code by setting CatchAccessDeniedException value to true.
Following code snippet shows how to handle access denied exception:

bool catchException = SPSecurity.CatchAccessDeniedException;
SPSecurity.CatchAccessDeniedException = false;
try
{
//updating list item
SPList list = SPcontext.Current.Web.List["TestList"];
SPListItem item = list.Items[0];
item["title"] = "Some value";
//If user doesnt have permission, exception will be thrown
//If value of CatchAccessDeniedException is true, then user will be
//redirected to AccessDenied.aspx page
item.Update();
}
cach(Exception ex)
{
//Your custom error message can be shown here
}
finally
{
//reset the flag to original value
SPSecurity.CatchAccessDeniedException = catchException;
}