c# - TempData null in asp.net core

Question

I am trying to use TempData in asp.net core However I am getting a null value on the get method of TempData. Can anyone please let me know how can I use TempData in asp.net core

Below are the things I, have added as per the research.

Project.json file

{
  "dependencies": {
    "Microsoft.NETCore.App": {
      "version": "1.0.1",
      "type": "platform"
    },
    "Microsoft.AspNetCore.Mvc": "1.0.1",
    "Microsoft.AspNetCore.Routing": "1.0.1",
    "Microsoft.AspNetCore.Server.IISIntegration": "1.0.0",
    "Microsoft.AspNetCore.Server.Kestrel": "1.0.1",
    "Microsoft.Extensions.Configuration.EnvironmentVariables": "1.0.0",
    "Microsoft.Extensions.Configuration.FileExtensions": "1.0.0",
    "Microsoft.Extensions.Configuration.Json": "1.0.0",
    "Microsoft.Extensions.Logging": "1.1.0",
    "Microsoft.Extensions.Logging.Console": "1.0.0",
    "Microsoft.Extensions.Logging.Debug": "1.0.0",
    "Microsoft.Extensions.Options.ConfigurationExtensions": "1.0.0",
    "Microsoft.EntityFrameworkCore.SqlServer": "1.1.0",
    "Microsoft.EntityFrameworkCore.Tools": "1.1.0-preview4-final",
    "Microsoft.EntityFrameworkCore.Design": "1.1.0",
    "Microsoft.EntityFrameworkCore.SqlServer.Design": "1.1.0",
    "DataBase": "1.0.0-*",
    "UnitOfWork": "1.0.0-*",
    "ViewModel": "1.0.0-*",
    "Common": "1.0.0-*",
    "System.IdentityModel.Tokens.Jwt": "5.0.0",
    "Microsoft.AspNetCore.Authentication.JwtBearer": "1.0.0",
    "Microsoft.AspNetCore.Diagnostics": "1.0.0",
    "Microsoft.AspNetCore.StaticFiles": "1.0.0",
    "Microsoft.AspNetCore.Session": "1.1.0",
    "Microsoft.Extensions.Caching.Memory": "1.1.0"
  },

  "tools": {
    "Microsoft.AspNetCore.Server.IISIntegration.Tools": "1.0.0-preview2-final",
    "Microsoft.EntityFrameworkCore.Tools.DotNet": "1.0.0-preview3-final",
    "Microsoft.AspNetCore.Razor.Tools": "1.0.0-preview2-final"
  },

  "frameworks": {
    "netcoreapp1.0": {
      "imports": [
        "dotnet5.6",
        "portable-net45+win8"
      ]
    }
  },

  "buildOptions": {
    "emitEntryPoint": true,
    "preserveCompilationContext": true
  },

  "runtimeOptions": {
    "configProperties": {
      "System.GC.Server": true
    }
  },

  "publishOptions": {
    "include": [
      "wwwroot",
      "**/*.cshtml",
      "appsettings.json",
      "web.config"
    ]
  },

  "scripts": {
    "postpublish": [ "dotnet publish-iis --publish-folder %publish:OutputPath% --framework %publish:FullTargetFramework%" ]
  }
}

start.cs file

public void ConfigureServices(IServiceCollection services)
{
    services.AddMemoryCache();
    services.AddSession();
    // Add framework services.
    services.AddMvc();
    services.AddTransient<IMarketUOW, MarketUow>();
    services.AddTransient<ICategoryUow, CategoryUow>();
    services.AddTransient<IUserProfileUow, UserProfileUow>();
    services.AddTransient<IItemUow, ItemUow>();

    services.AddTransient(typeof(IGenericRepository<>), typeof(GenericRepository<>));
    var connection = Configuration.GetConnectionString("DefaultConnection");
    services.AddDbContext<EmakitiContext>(options => options.UseSqlServer(connection));
}
public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
    app.UseSession();
    app.UseMvc(routes =>
    {
        routes.MapRoute(
            name: "default",
            template: "{controller=Home}/{action=Index}/{id?}");
        });
    }

Here is the implementation of tempdata.When this method is called I can see the value in TempData.

[HttpGet("{pageNumber}")]
public GenericResponseObject<List<MarketViewModel>> GetMarketList(int pageNumber)
{
    TempData["Currentpage"] = pageNumber;
    TempData.Keep("Currentpage");
    GenericResponseObject<List<MarketViewModel>> genericResponseObject = new GenericResponseObject<List<MarketViewModel>>();
    genericResponseObject.IsSuccess = false;
    genericResponseObject.Message = ConstaintStingValue.Tag_ConnectionFailed;
    try
    {
        var marketItem = _iMarketUow.GetMarketList(pageNumber);
        genericResponseObject.Data = marketItem.Item1;
        var totalPages = (int)Math.Ceiling((decimal)marketItem.Item2 / (decimal)10);
        genericResponseObject.TotalPage = totalPages;
        genericResponseObject.IsSuccess = true;
        genericResponseObject.Message = ConstaintStingValue.Tag_SuccessMessageRecord;
        genericResponseObject.Message = ConstaintStingValue.Tag_ConnectionSuccess;
    }
    catch (Exception exception)
    {
        genericResponseObject.IsSuccess = false;
        genericResponseObject.Message = exception.Message;
        genericResponseObject.ErrorCode = exception.HResult;
        genericResponseObject.ExceptionErrorMessage = exception.StackTrace;
    }
    return genericResponseObject;
}

But the below method has null value in the temp data.

[HttpPost]
public GenericResponseObject<List<MarketViewModel>> AddUpdateMarket([FromBody] MarketViewModel marketViewModel)
{
    GenericResponseObject<List<MarketViewModel>> genericResponseObject = new GenericResponseObject<List<MarketViewModel>>();
    genericResponseObject.IsSuccess = false;
    genericResponseObject.Message = ConstaintStingValue.Tag_ConnectionFailed;

    if (marketViewModel!= null && ModelState.IsValid)
    {
        try
        {
            _iMarketUow.AddUpdateMarketList(marketViewModel);
            genericResponseObject = GetMarketList(Convert.ToInt16(TempData.Peek("Currentpage")));
        }
        catch (Exception exception)
        {
            genericResponseObject.IsSuccess = false;
            genericResponseObject.Message = exception.Message;
            genericResponseObject.ErrorCode = exception.HResult;
            genericResponseObject.ExceptionErrorMessage = exception.StackTrace;
        }
    }
    else
    {
        genericResponseObject.Message = ConstaintStingValue.Tag_InputDataFormatNotMatch;
    }
    return genericResponseObject;
}

Here is the image of the debug session

Answer 1

Edited:

As Described in https://docs.microsoft.com/en-us/aspnet/core/security/gdpr?view=aspnetcore-2.2#tempdata-provider-and-session-state-cookies-arent-essential by default TempData cookies are removed by the CookiePolicy Middleware. this can be changed by putting this in Startup.ConfigureServices():

// The TempData provider cookie is not essential. Make it essential
// so TempData is functional when tracking is disabled.
services.Configure<CookieTempDataProviderOptions>(options => {
    options.Cookie.IsEssential = true;
}); 

=============================================

Old Answer:

After Migrating to ASP Core 2.1 I had this issue and after working for a day find the solution:

in Startup.Configure() app.UseCookiePolicy(); should be after app.UseMVC();