Am I structuring my Razor app "correctly"? - razor

Question

I'm building my first razor app and am wondering if I'm organizing my files in a good way (one that will be clear if other people were to look at my code, and one that will not inhibit performance). My main concern is with library-like functions that I plan to use throughout the app. For those I've been storing string formatting functions and the like in the "App_Code" folder--for example I have the below function stored in a class there:
public static decimal? ToDecimal(object? val) => (val is DBNull) ? (decimal?)null : Convert.ToDecimal(val);
Additionally I plan to user a "Helpers" folder to store any HTML that will need to be repeated throughout the app. Are these the correct places to put this kind of stuff?
And then my bigger question is for data retrieval/storage. Say I have a "Location" class which is tied to a SQL table. If I were using EF, to retrieve and store data is one command, but in my case I'm writing my own functions to get the data. Right now I have all that code on the Index page for the Location (retrieving all locations and the various linked files), but now I need to re-use a lot of those functions on the edit & view pages for a single location. Where is the right place to store those general functions (e.g. GetLocation(id), GetAllLocations, etc.)? Would it make sense to just make a random "Library" folder and put them in a class there, having a dedicated file for each class I need to interact with? Just throw it in App_Code?
A good example of the last one is this function, where I retrieve all States from the database. I expect to need to do this on multiple pages--where should I store it?
private void GetStates()
{
int id;
string DbQuery = "SELECT StateId,Abbreviation,StateName " +
"FROM [dbo].[State] " +
"WHERE RowStatus<>0 ";
States = new Dictionary<int, State>();
SqlCommand DbCommand = new SqlCommand(DbQuery, DbConnection);
SqlDataReader dataReader = DbCommand.ExecuteReader();
while (dataReader.Read())
{
id = Convert.ToInt32(dataReader[0]);
States.Add(id, new State()
{
StateId = id,
Abbreviation = Convert.ToString(dataReader[1]),
StateName = Convert.ToString(dataReader[2])
});
}
dataReader.Close();
DbCommand.Dispose();
}

Answer 1

If you have an App_Code folder, you have an ASP.NET Web Pages app, not a Razor Pages app, as this question has been tagged. Web Pages is an old framework that hasn't seen any updates for years and is based on the old .NET Framework Website Project type as opposed to the Web Application project type which requires compilation before deployment.
All C# code has to go in the App_Code folder or in separate class libraries which have to be manually added to the bin folder. In short ASP.NET Web Pages is not a good choice if you are concerned about code organisation (or much else if you are also concerned about performance, cross platform deployment, framework updates, extensibility, testing etc). You should look at Razor Pages instead: https://www.learnrazorpages.com/razor-pages/tutorial/bakery