Application settings

Question

I am using the user.application both programmatically and by the project.properties.settings feature. While user settings are quite simple the application settings are more tricky as they can not be directly set programatically (write protetced) and when starting the application the application settings are automatically loaded. It it unclear (to me) at what point in the startup process this happnes. It is unclear how and when I am supposed to instantiate the objects that are then set or modified by the automatic setting. Can someone who has good understanding of the application setting help me get better understanding? (Could not find answer to my question on the web) Thanks Samtal

Vulpes · Answer

When you create either a user or an application setting a file called Settings.Designer.cs is created which stores these settings along with another file called Settings.cs. These files can be opened from Solution Explorer. If you look at the code generated for Settings.Desiger.cs you'll see that application settings are represented by read-only properties and user settings by read/write properties. Settings.cs enables you to add event handling code to deal with changes to these settings. When your application is compiled these files are compiled with it as part of the overall source code. The settings are therefore available as soon as the application starts. You don't have to create an instance of the Properties.Settings class yourself because as soon as you access its static Default property this gives you access to a default instance which you can then use to access the settings themselves.

Sam · Answer

Thanks for your efforts. The funny thing is that I can easily save a dataset as user setting (as xml). Works like charm. So why not App setting? I can find a workaround to preserve my data but it will necessitate additional user steps (I anyhow use Excel file as the dataset source). I did not yet give up and will try harder at later time. Will let you know. samtal

Vulpes · Answer

After playing around with this myself to see if I could come up with anything that might help I'm beginning to wonder whether its actually possible to use a DataSet as an application setting. Although creating a strongly typed DataSet (DataSet1) and associating a DataTable with it was no problem at design time I couldn't then find any obvious way to use this as a type for an application setting - only the generic System.Data.DataSet could be used. If I then tried to add something like: new DataSet1() in the value column I was informed that it can't be converted to System.Data.DataSet even though it's derived from it! Is it really necessary to use a DataSet as the actual setting. Could you just store a connection string and a query which enables you to generate it at runtime instead?

Sam · Answer

As so far the replies where of generic nature (due to my too generic question) I will be more specific with the problem I am having as follows: Using VS2010 Express Win7-64. In my application I Have several Application settings. Most (mixed types) are User Settings one is Application Setting (a DataSet). I use the built-in Settings table where the one setting scope is set as Application while the others scope is User. The User settings are all saved and retrieved OK and can also be seen in the XML file. (string userConfig = ConfigurationManager.OpenExeConfiguration( ConfigurationUserLevel.PerUserRoamingAndLocal).FilePath;) Problem: While the User settings are saved OK the one Application Setting is not saved and is not present in the relevant config file. (string appConfig = ConfigurationManager.OpenExeConfiguration( ConfigurationUserLevel.None).FilePath;). In the Settings.Design file we can see the Application Setting as read-only item (get only) which is OK but no data is saved and no data is found (except a null DataSet). There is similar DataSet in the User settings that is saved OK and can be loaded. To save the settings I run: Properties.Settings.Default.Upgrade(); Properties.Settings.Default.Save(); Thanks

Vulpes · Answer

Well DataSets are XML serializable so you should certainly be able to use them as application settings. If you still have VS 2008 it might be an idea to add a DataSet setting again to a new project check you can retrieve it OK and then try and reproduce the same steps in your VS 2010 project just in case you missed something the first time.

Sam · Answer

Thank you Vulpes for your detailed (and quick!) reply. While it is all true yet it is not clear to me how a setting is treated at startup in particular an application setting. I can easily define preserve and retrieve user settings be it strings or datasets. I do it with the help of the Settings.setting class and associated table where I set the scope to User  and then manipulate programatically as required (both saving and retrieving). When I set the scope to Application I can see the specific setting in the Settings.Designer as read-only (Get only) but I can not get it back after startup (example: this.fareDataSet = Properties.Settings.Default.fareDataSet; will returns a null DataSet. I made sure I have the full dataset object upon closing and saving but it is lost somewhere when I close the form or reopen it. In previous versions of VS2008 I remember I could save the application scope and I could even see the detailed html dataset file which I can not locate with my current VS2010. Any idea or advise? Thanks.