尝试运行ASP.NET核心web API项目时出现错误NU1605

我已经创建了一个ASP.NET核心API,并按如下方式定义了我的控制器:

[Route("api/[controller]")]
[ApiController]
public class SignUpController : ControllerBase
{
    private readonly DNNContext _context;

    public SignUpController(DNNContext context)
    {
        _context = context;
        var merchantSignUpResponse = PutResponse();
    }

    [HttpPut("{id}")]
    public async Task<IActionResult> PutResultAsync(int id, [FromBody]ProPaySignUp signUp)
    {
        try
        {
            await _context.SignUpResponses.AddAsync(PutResponse());
            await _context.SaveChangesAsync();
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
        }

        return Accepted();
    }


    public SignupResponse PutResponse()
    {
        string url = "https://xmltest.propay.com/api/propayapi/";
        var credentials = GetCredentials();
        var request = BuildMerchantData();
        var restRequest = CreateRestRequest("/Signup", Method.PUT);
        restRequest.AddJsonBody(request);
        return Execute<SignupResponse>(restRequest, url);
    }
    private static RestRequest CreateRestRequest(string resource, Method method)
    {
        var credentials = GetCredentials();

        var restRequest = new RestRequest
        {
            Resource = resource,
            Method = method,
            RequestFormat = DataFormat.Json,
        };
        restRequest.AddHeader("accept", "application/json");
        restRequest.AddHeader("Authorization", credentials);
        return restRequest;
    }

     private static T Execute<T>(IRestRequest request, string baseUrl) where T : class, new()
    {
        var client = new RestClient(baseUrl);
        var response = client.Execute<T>(request);

        if (response.ErrorException != null)
        {
            Console.WriteLine(
                "Error: Exception: {0}, Headers: {1}, Content: {2}, Status Code: {3}",
                response.ErrorException,
                response.Headers,
                response.Content,
                response.StatusCode);
        }

        return response.Data;
    }

解决方案成功构建。然后我启动Postman并输入URL https://localhost:44381/api/SignUp There was an error connecting to https://localhost:44381/api/SignUp.

然后,我在我的项目所在的目录下打开了一个命令提示符并执行了它 dotnet run SOBProPayService . 返回的错误是

error NU1605: Detected package downgrade: Microsoft.AspNetCore.Razor.Design from 2.2.0 to 2.1.2. Reference the package directly from the project to select a different version.

如何解决此错误?