Transient service with a function that runs only for the first request-CodePudding

In my asp.net core 6 mvc project, I have a transient service ContentService. This service is inherited from IContentService and added to Program.cs using

builder.Services.AddTransient<IContentService, ContentService>();

Here is the implementation of the service:

public interface IContentService
{
    public string GetText(int id);
}

public class ContentService : IContentService
{
    private readonly ContentDbContext _context;
    private List<string> textList;

    public ContentService(ContentDbContext context)
    {
        _context = context;

        ReadTexts();
    }

    public void ReadTexts()
    {
        // Reads text from the database and fills the textList.
        // THIS CODE MUST RUN ONLY FOR THE FIRST REQUEST.
    }

    public string GetText(int id)
    {
        return textList(id);
    }
}

The problem is every time ContentService is requested, the constructor runs and ReadTexts() is called, which is a heavy function that must only run for the first request. Is there anyway to implement a transient service with a code block that runs only for the first request? Note that I cannot use AddSingleton.

CodePudding user response：

You have to make textList as static if you want it to hold data which should be read only on first request.

try this.

public class ContentService : IContentService
{
    private readonly ContentDbContext _context;
    private static List<string> textList = new List<string>();

    public ContentService(ContentDbContext context)
    {
        _context = context;

        ReadTexts();
    }

    public void ReadTexts()
    {
       if(!textList.Any())
       {
        // Reads text from the database and fills the textList.
        // THIS CODE MUST RUN ONLY FOR THE FIRST REQUEST.
       }
    }

    public string GetText(int id)
    {
        return textList(id);
    }
}