Develop Reference

Open file directly from SharePoint path with CSOM

I have a SharePoint server and I want to open files directly from the Server with SharePoint CSOM.
User clicks button --> the file (Excel, Word, ...) opens at the client machine with the standard software.
Directly means, that if I change something to the file and click save, that the file is directly saved on the SharePoint server (or if I click e.g. 'Save as' in Excel the suggested path is 'https://sharpoint.url.com/folder').
Actually I have:
using Microsoft.SharePoint.Client;
var clientContext = new ClientContext("https://sharpoint.url.com");
string relativePath = "/folder/file.xls";
clientContext.Credentials = CredentialCache.DefaultCredentials;
var file = clientContext.Web.GetFileByServerRelativeUrl(relativePath);
clientContext.Load(file);
clientContext.ExecuteQuery();
What do I have to do now, if I want to open the file directly (no download)?

I assume you ask how to access the file's stream instead of downloading it to a local folder.
You can use the File.OpenBinaryDirect method to get access to its ETag and stream, eg :
using(var fileInfo=File.OpenBinaryDirect(clientContext,"/folder/file.xls"))
using(var reader=new StreamReader(fileInfo.Stream))
{
//Do whatever you want with the data
}
BTW you shouldn't use the old xls files. The format is deprecated for over 10 years. The current Excel format, xlsx, is a zipped package of XML files that's better supported by SharePoint itself, doesn't require Excel to generate or read.
For example, if you wanted to read cell values from an xlsx file, you could use the popular EPPlus library to read directly from the stream:
using(var fileInfo=File.OpenBinaryDirect(clientContext,"/folder/file.xlsx"))
using(var package=new ExcelPackage(fileInfo.Stream))
{
var sheet=package.Workbook.Worksheets[0];
var value=ws.Cells["A1"].Value;
//...
}
UPDATE
It seems the question isn't related to programming after all. All that's needed to save or open a SharePoint document is clicking on the document's link. What happens then depends on the Open Documents in Client Applications setting at the site and document library level.
This affects the headers the server sends to the browser when the user clicks on a document link. The browser may still refuse to open the registered application and display the Save dialog.
If that doesn't work, you should check why instead of writing code. It's probably a configuration error or a browser setting. Solving it is easier than creating workarounds, pushing them to all client machines. And then keeping track of all the patches, where they are deployed and deploying new ones.
Apart from that, the Office applications know about SharePoint and document libraries since 2003. They can browse them, display SharePoint properties for the document, show collaborators etc.
As I mentioned in the question comments, a lot of what people think as "SharePoint Developoment" is nothing more that configuration, administration and end user features.
MSDN docs don't help either - they actually cause harm by not covering SP administration or explaining the features and how they are used. You'll find that in Technet. For years, people created webparts in code to change how grids looked because MSDN didn't explain how eg the DataViewWebPart worked or how you could style a grid from the UI.
In general, the best place for such questions is http://sharepoint.stackexchange.com. For example, check “Open in the client application” Vs “Use the server default (Open in the client application)” inside the document library advance settings

We can create Map Network Drive for SharePoint library, and open the file from the network location. Check article below:
http://support.sherweb.com/Faqs/Show/how-to-connect-to-a-sharepoint-site-using-webdav-sharepoint-2013
Or we can download the file from SharePoint and open it using the code below:
Application.Workbooks.Open(#"C:\Test\YourWorkbook.xlsx");
Reference: https://msdn.microsoft.com/en-us/library/b3k79a5x.aspx

Opening file with Process.Start starts process but does not open window

I am trying to open a document with Process.Start in an ASP.NET web application. In this case, I am opening a Word file (.docx), but will be opening any type of file in the future.
My understanding of Process.Start is that the application is determined from the extension of the file path passed as a parameter, and opened.
The code I am using is very simple:
Process.Start("C:\\test.docx");
The file exists, and I am not getting any exceptions when the code is run. However, Word is not opening.
I have monitored my running processes through task manager whilst the code is running, and have noticed that a WINWORD.EXE process is starting with the User Name of the application pool being used (DefaultAppPool) in this case.
Why would the process be starting, but no Word window opening?
Edit: In case there is a better solution, here is my situation:
I am allowing users to upload documents, which are saved in an Oracle database as a BLOB. The user is then able to view their saved documents, and open them. What is the best way to extract a byte array from a BLOB, and open it using the correct application?

How to save the XML files in Computer?

In my project my app receives an XML from another program. I want to save this XML file in the folder in my PC. But if there is another XML file that will come, the XML will be added in the folder not overwrite the existing XML. How can I achieve it?
I am using this code right now but I don't know why I got an access denied error.
System.IO.File.WriteAllText(#"C:\XML", abc);

First of all, the error that you receive is because of Windows UAC which denies users without Administrator privileges to write on the C:\ disk. Create a folder in which you have access, for example "c:\temp\" and write your files in there.
Also, you specify a file and not folder.
And if you don't want to overwrite the file, just make sure to generate a unique filename (a guid perhaps).

Word File savings without closing are Not Uploaded to the server

In my case, I want to build my own "drop box" like application which I am going to use as a part of my another project.
Discription:
When a word file is opened in the "drop box" folder(inside the folder where changes to the files, file creations deletions ect.. are identified). pictures, txts, txt updates are uploaded to the server without any issue.
But when it comes to office documents. office document creation is uploaded.
Problem:
when the word file is opened, and do some update and save it. the file can not be uploaded due to permission error. even the opened file can not be copied to another place and then uploaded.
Any one faced this kind of issue, and any sugessions.
But we can manually copy and save a opened and saved(but not closed) to another location
But in the program it is not allowed.

You can create another copy of file, this is important because uploading may be slower and reading shared file may lead to conflicts for Word, so what you can do is, you can create a copy quickly on temp file and upload the temp file.
string tmp = Path.GetTempFileName();
using(Stream s = new FileStream(filePath,
FileMode.Open, FileAccess.Read,
// following option will let you open
// opened file by other process
FileShare.ReadWrite)){
using(FileStream fs = File.OpenWrite(tmp)){
// this will copy file to tmp
s.CopyTo(fs);
}
}
// upload tmp file...

your problem is similar to what we faced. In our case we are all connected to a domain directory and the problem was the antivirus installed on our server gives read/write permissions to users (executing exe, installing apps). so you specifically need to give a user the right to execute an app that wants to use another app, in this case office docs.
The problem extended to asp apps using Crystal Reports. hope it helps.

Can't delete a file from a client after uploading it to the server

I'm using asp:FileUpload control to upload a file to the server. Nothing fancy there, just
FileUploadId.Save();
File gets uploaded successfully, and everything is fine until I try to delete that file on the CLIENT. I get a good-old "File is being used by another person or program" message.
How do I make sure that file is not being accessed on the client after it's been uploaded?
EDIT
deleting the file has nothing to do with the application. i'm just trying to delete the file manually since i don't need it any more.
EDIT2
closing the browser fixed the problem ... any ideas?

Since the problem happens both in IE and FF: could it be that the file is locked by some AntiVirus software?

The issue might be the file can be locked by the aspnet process even after uploading. Once you close the IE, the aspnet process release the file

How are you trying to delete the file at the client? Unless you're hosting in WebBrowser, or using something like an ActiveX control, you only have javascript at the client - and that doesn't provide random file access.
So: what is the full setup here?

A thought. It may not be the file upload that is causing the problem. As the surrounding code isn't posted it's difficult to tell, but, for example, do you have a Zip manager object of some kind that you're not disposing of?