A SystemFileWatcher is running and delegate execution using reflection, the system perform multiple kind of actions,including data import into MongoDB since 2 years. The system suddenly start freezing when handling MongoDB import. This occurs after switching the project to .NET Framework 4.5 .
I never find any way to predict the freezing behavior and restarting the application allow to continue the processing.

Please find hereafter the failing code: no exception triggered, only apps freezing.

public bool Save(MongoCollection col, bool replace)
{
this.CountSet++;
if (Id == ObjectId.Empty)

{ MongoGridFSFileInfo gridFsInfo = col.Database.GridFS.Upload(LocalFilename, this.Name + this.Ext); this.Id = gridFsInfo.Id.AsObjectId; col.Save(this,WriteConcern.Acknowledged); }

else
{
if (replace)
{
using (var fs = new FileStream(LocalFilename,
FileMode.Open))

{ col.Database.GridFS.DeleteById(Id); MongoGridFSCreateOptions opt = new MongoGridFSCreateOptions(); opt.Id = Id; MongoGridFSFileInfo gridFsInfo = col.Database.GridFS.Upload(fs, this.Name + this.Ext, opt); }

}
col.Save(this, WriteConcern.Acknowledged);
}
return true;
}