Provider Hosted App – Copy Document across Site Collections

To copy documents across site collections in provider hosted app, we need to perform the following steps:

  1. Provide appropriate permissions to app
  2. Create client context for the source location
  3. Downloading document stream from source
  4. Create client context for the destination
  5. Uploading document to destination (This step is same as mentined in my previous post)

The approach I am going to display will also help if you want to create another site collection context from the existing one.

For the above scenario, please note the following points:

  1. App should have minimum “Write” permission on “Tenant” for the code to work as we are moving document from one site collection to another.
  2. I have used app-only policy. This is used as user might not have write permission on the whole tenant. The only downside is, in “Created By” field, instead of user name, it shows “SharePoint App”. I created a custom column to save actual user name.

Hope this helps. Happy coding!!

 

CSOM – Check If My Site Exists

There are times when we want to know whether My Site exist for a particular user. In general, My Site is created when a user accesses the My Site (i.e. the “About Me” link) for the first time. For more details on My Site architecture check this msdn link.

Using CSOM, we can fetch a particular user’s my site link. The code for that is:

The above code returns my site url of the user but if my site does not exist then also it returns the my site host url of that user. So, in this case the url returned is something like:

https://tenant-my.sharepoint.com/Person.aspx?accountname=accountnameofuser

This does not tell us whether my site actually exist or not unless we do some url manipulation. But there is a peroperty in the same code which returns my site relative url only if it exists and that property is PersonalSpace. This is present in UserProfileProperties of PeopleManager class.

The code to fetch that is :

This will return blank if my site does not exist else will return /personal/email_of_user

P.S. The code above could also be used in apps, just give Read permission to User Profile.

Happy Coding!!

Provider Hosted App – Upload Large Files using CSOM

We all at some time struggled with uploading large files using CSOM in O365. Using managed client object model, we can upload a maximum of 2MB file size. If the file is of larger size, we usually had two options:

  1. File.SaveBinaryDirect
  2. Using REST which supports upto 2GB

The first option can not be used in Sharepoint Online because SaveBinaryDirect does not work with claims authentication (check this link).

Update: We can now use SaveBinaryDirect in SP Online by using SharePointOnlineCredentials class which could be used for authentication of context but I am yet not able to make it work in provider hosted add-in. It works in normal console app by providing credentials though.

Does that mean we are left with REST only? Actually NO. We have one more way by which we can upload files greater than 2MB in O365 using CSOM in provider hosted app. But let’s first see the standard CSOM way which allows us 2MB file upload.

Now the method to upload larger files is exactly the same. We only have to use FileCreationInformation.ContentStream property instead of FileCreationInformation.Content property. The whole code is present below:

In some cases, you might get a FileNotFoundException while using above code. Below is another way to use the code

Note that I replaced FileStream with the input stream present in the uploaded file itself.

P.S. I have tested the above code for files upto 50 MB. It depends largely on internet speed. Once for 50MB file size it gave me time out error (which could be fixed by setting RequestTimeout property of client context)

Hope this helps.

Reference:

  1. O365 AMS

Unique Identifier for O365

Multi-tenant apps are a very common scenario in real world. Whenever we create an app, we mostly target it to multiple tenants for wider reach. There are some cases in which we want to save our app data in custom database instead of app web or host web. These scenarios are very frequent and at that time we need a unique identifier to differentiate among tenants. So my search started for a pre-existing identifier of O365 and ended right at TokenHelper.cs file.
Yes, Microsoft has already provided a code for it, I just didn’t realize it’s a unique identifier. 🙂

In TokenHelper.cs there is a public method GetRealmFromTargetUrl(Uri targetApplicationUri) that takes URI of the target sharepoint site as its parameter. This method actually return a string representation of the realm GUID. According to msdn,

 Realm is unique to each tenant in Office 365 or to each SharePoint farm on-premises. It is possible to discover the realm at run time. So, it is not necessary to cache this information between requests, but it will cost you an extra round trip to SharePoint each time you want to look it up. If you use code similar toTokenHelper.GetRealmFromTargetUrl with the site URL, and cache the result per site (or even per site and per user), you can use this later without making the extra call.

For more details, visit this link.

Therefore, above method return a unique id for tenant. You can pass host web uri in it. This id can be saved in database for further use and can even be cached.

Source code for this method is given below. This is copy pasted from TokenHelper.cs class which Visual Studio auto-generates on creating provider hosted app.

 


public static string GetRealmFromTargetUrl(Uri targetApplicationUri)
{
WebRequest request = WebRequest.Create(targetApplicationUri + "/_vti_bin/client.svc");
request.Headers.Add("Authorization: Bearer ");

try
{
using (request.GetResponse())
{
}
}
catch (WebException e)
{
if (e.Response == null)
{
return null;
}

string bearerResponseHeader = e.Response.Headers["WWW-Authenticate"];
if (string.IsNullOrEmpty(bearerResponseHeader))
{
return null;
}

const string bearer = "Bearer realm=\"";
int bearerIndex = bearerResponseHeader.IndexOf(bearer, StringComparison.Ordinal);
if (bearerIndex < 0)
{
return null;
}

int realmIndex = bearerIndex + bearer.Length;

if (bearerResponseHeader.Length >= realmIndex + 36)
{
string targetRealm = bearerResponseHeader.Substring(realmIndex, 36);

Guid realmGuid;

if (Guid.TryParse(targetRealm, out realmGuid))
{
return targetRealm;
}
}
}
return null;
}

 

Hope this helps. 🙂