Hi @Konstantin Hvan ,
I'm glad to hear you solve the problem ,if you have any issue about SharePoint, you are welcome to raise a ticket in this forum.
By the way, since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others." and according to the scenario introduced here: Answering your own questions on Microsoft Q&A, I would make a brief summary of this thread:
[CSOM: Microsoft.SharePoint.Client.ServerException: No User or App Context found]
Issue Symptom:
I've got the exception when using SharePoint Search API:
Microsoft.SharePoint.Client.ServerException: No User or App Context found
my code works fine on one SharePoint site, but on another it fails with above error.
My code is just a simple search query:
KeywordQuery keywordQuery = new KeywordQuery(_context);
keywordQuery.StartRow = startIndex;
keywordQuery.QueryText = $"IsDocument:1";
keywordQuery.RowLimit = _searchPagesChunkLimit;
keywordQuery.RowsPerPage = _searchPagesChunkLimit;
keywordQuery.TrimDuplicates = false;
SearchExecutor searchExecutor = new SearchExecutor(_context);
ClientResult<ResultTableCollection> results = searchExecutor.ExecuteQuery(keywordQuery);
_context.ExecuteQuery();
Current status:
The application lacks rights, specifically it's Sites.ReadAll
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