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CC#DIAdiscord.js - Imagine an app DTDrizzle Team

•Created by Spaxter on 8/9/2024 in #help

✅ Transient DbContext vs DbContextFactory

In EF Core, what is the difference between registering a transient DbContext vs a DbContextFactory for DI? In both cases the DbContext will be created on-demand and disposed when the operation is completed, right? Are there any clear indications on when to use which?

4 replies

CC#

•Created by Spaxter on 6/19/2024 in #help

✅ EF Core - Not getting updated data from PostgreSQL table

I have the following method in my DbService.cs

public async Task<long?> GetLastDumpTimeStamp(string endpoint)
{
    using (var context = await _dbContextFactory.CreateDbContextAsync())
    {
        DumpHistory? history = await context.DumpHistory.AsNoTracking().Where(row => row.Endpoint == endpoint).FirstOrDefaultAsync();
        return history?.LastUpdate;
    }
}

public async Task<long?> GetLastDumpTimeStamp(string endpoint)
{
    using (var context = await _dbContextFactory.CreateDbContextAsync())
    {
        DumpHistory? history = await context.DumpHistory.AsNoTracking().Where(row => row.Endpoint == endpoint).FirstOrDefaultAsync();
        return history?.LastUpdate;
    }
}

Which returns a unix timestamp from a postgres table. However if I manually change the data in the column to a completely different number and call the method again I still get the old value prior to my manual change, even after restarting my app. Am I doing something wrong?

6 replies

CC#

•Created by Spaxter on 6/18/2024 in #help

Method on DI service doesn't do anything

Hello, I have a .NET app using Dependency Injection. One of the services I am injecting is a service for handling database insertions etc. Right now I have two methods on this class, one of them works perfectly fine but the other doesn't do anything when called. This is the method:

public async Task ClearGames()
    {
        _logger.LogDebug("ClearGames called");
        using (var context = await _dbContextFactory.CreateDbContextAsync())
        {
            _logger.LogDebug("Truncating games table...");
            try 
            {
                await context.TruncateAsync<DbGame>();
                await context.SaveChangesAsync();
            } catch (Exception e)
            {
                _logger.LogError("{error}", e);
                throw;
            }
            _logger.LogDebug("Truncate finished");
        }
    }

public async Task ClearGames()
    {
        _logger.LogDebug("ClearGames called");
        using (var context = await _dbContextFactory.CreateDbContextAsync())
        {
            _logger.LogDebug("Truncating games table...");
            try 
            {
                await context.TruncateAsync<DbGame>();
                await context.SaveChangesAsync();
            } catch (Exception e)
            {
                _logger.LogError("{error}", e);
                throw;
            }
            _logger.LogDebug("Truncate finished");
        }
    }

And when calling them like this, I only see the debug logs from the second method. The first one doesn't seem to run at all despite being called

await _db.ClearGames();
await _db.InsertGames(games);

await _db.ClearGames();
await _db.InsertGames(games);

20 replies

CC#

•Created by Spaxter on 6/17/2024 in #help

DbContextFactory check for valid connection on app startup

I have a .NET app where I'm currently using EF Core's DbContextFactory with Postgres. However I noticed that no matter what host I set in my connection string the app starts normally and no errors are thrown. Is it possible to validate the connection at startup?

builder.Services.AddDbContextFactory<DataContext>(options => 
{
    options.UseNpgsql(postgresOptions.ConnectionString);
}

builder.Services.AddDbContextFactory<DataContext>(options => 
{
    options.UseNpgsql(postgresOptions.ConnectionString);
}

2 replies

CC#

•Created by Spaxter on 10/18/2023 in #help

✅ EF Core long running query causing concurrency issues

Hello. I have a .NET application that uses a DbContext with PostgreSQL. To test the performance of my app, I added a million rows to one of the tables. I noticed that it takes a pretty long time to fetch all of these rows, and if I run the method to get all the rows again before the previous query finishes, it throws the following exception:

System.InvalidOperationException: A second operation was started on this context instance before a previous operation completed. This is usually caused by different threads concurrently using the same instance of DbContext.

This is an example of how it is set up currently:

private MyDbContext _dbContext;

public DbService(MyDbContext dbContext)
{
  _dbContext = dbContext ?? throw new ArgumentNullException(nameof(dbContext));
}

// This method throws the excpetion if called again before the previous query is finished
public async Task<List<MyObj>> GetAllObjects()
{
  return await _dbContext.MyTable.AsNoTracking().ToListAsync();
}

private MyDbContext _dbContext;

public DbService(MyDbContext dbContext)
{
  _dbContext = dbContext ?? throw new ArgumentNullException(nameof(dbContext));
}

// This method throws the excpetion if called again before the previous query is finished
public async Task<List<MyObj>> GetAllObjects()
{
  return await _dbContext.MyTable.AsNoTracking().ToListAsync();
}

9 replies

CC#

•Created by Spaxter on 10/14/2023 in #help

✅ launchSettings.json being ignored completely

All of a sudden, my .NET Visual Studio project has stopped respecting my launchSettings.json file. No matter what profile I run the app with, it uses the ports 5000 and 5001. I have no idea how this happened or why. launchSettings.json

{
    "IIS Express": {
      "commandName": "IISExpress",
      "launchBrowser": true,
      "launchUrl": "swagger",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    },
    "Docker": {
      "commandName": "Docker",
      "launchBrowser": true,
      "launchUrl": "{Scheme}://{ServiceHost}:{ServicePort}/swagger",
      "publishAllPorts": true,
      "useSSL": true
    },
    "WSL": {
      "commandName": "WSL2",
      "launchBrowser": true,
      "launchUrl": "https://localhost:7272/swagger",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development",
        "ASPNETCORE_URLS": "https://localhost:7272;http://localhost:5109"
      },
      "distributionName": ""
    }
  },
  "$schema": "https://json.schemastore.org/launchsettings.json",
  "iisSettings": {
    "windowsAuthentication": false,
    "anonymousAuthentication": true,
    "iisExpress": {
      "applicationUrl": "http://localhost:48027",
      "sslPort": 44314
    }
  }
}

{
    "IIS Express": {
      "commandName": "IISExpress",
      "launchBrowser": true,
      "launchUrl": "swagger",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    },
    "Docker": {
      "commandName": "Docker",
      "launchBrowser": true,
      "launchUrl": "{Scheme}://{ServiceHost}:{ServicePort}/swagger",
      "publishAllPorts": true,
      "useSSL": true
    },
    "WSL": {
      "commandName": "WSL2",
      "launchBrowser": true,
      "launchUrl": "https://localhost:7272/swagger",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development",
        "ASPNETCORE_URLS": "https://localhost:7272;http://localhost:5109"
      },
      "distributionName": ""
    }
  },
  "$schema": "https://json.schemastore.org/launchsettings.json",
  "iisSettings": {
    "windowsAuthentication": false,
    "anonymousAuthentication": true,
    "iisExpress": {
      "applicationUrl": "http://localhost:48027",
      "sslPort": 44314
    }
  }
}

10 replies

CC#

•Created by Spaxter on 10/14/2023 in #help

✅ Unit Testing HttpClient

Hello, I'm currently trying to write some unit tests for a class that uses an HttpClientFactory through DI. This is the just of what I'm doing in these tests:

private string myApiUrl = "https://www.some-api.com";
private IHttpClientFactory _httpClientFactory;
private Mock<HttpMessageHandler> _httpClientMock;

[SetUp]
public void SetUp()
{
  _httpClientMock = new Mock<HttpMessageHandler>();
  _httpClientMock.SetupRequest(HttpMethod.Post, $"{myApiUrl}/example").ReturnsResponse("Example response");

  var httpClientFactoryMock = new Mock<IHttpClientFactory>();
  httpClientFactoryMock.Setup(c => c.CreateClient("exampleApi")).Returns(new HttpClient(_httpClientMock.Object)
  {
      BaseAddress = new Uri(myApiUrl)
  });
  
  _httpClientFactory = httpClientFactoryMock.Object;
}

private string myApiUrl = "https://www.some-api.com";
private IHttpClientFactory _httpClientFactory;
private Mock<HttpMessageHandler> _httpClientMock;

[SetUp]
public void SetUp()
{
  _httpClientMock = new Mock<HttpMessageHandler>();
  _httpClientMock.SetupRequest(HttpMethod.Post, $"{myApiUrl}/example").ReturnsResponse("Example response");

  var httpClientFactoryMock = new Mock<IHttpClientFactory>();
  httpClientFactoryMock.Setup(c => c.CreateClient("exampleApi")).Returns(new HttpClient(_httpClientMock.Object)
  {
      BaseAddress = new Uri(myApiUrl)
  });
  
  _httpClientFactory = httpClientFactoryMock.Object;
}

But every test that uses the IHttpClientFactory throws the following exception:

System.InvalidOperationException: Handler did not return a response message.

System.InvalidOperationException: Handler did not return a response message.

10 replies

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