MissingMethodException：没有为类型定义无参数构造函数

Question

我有一个使用 .net core 5 的 Blazor 应用程序。我正在尝试运行一个页面来触发电子邮件发送 (EmailSample)，在我尝试添加构造函数注入以记录错误之前，它工作正常。一旦我添加构造函数注入并重新运行页面，我就会收到 No parameterless constructor defined for type 错误。我没有正确使用它吗？如何修复，这样我就不会收到该错误。如果我能弄清楚如何在 Startup.cs/ConfigureServices/services.AddSingleton< ??? > 中添加记录器作为服务，我就可以解决这个问题然后在 EmailSample class 中执行 [Inject]，但不知道如何操作。

[Inject]
public ILogger _logger { get; set; }

导致错误的代码是...（注：设置为部分class，不在.razor页面@code{}）

public partial class EmailSample
{
    private readonly ILogger<EmailSample> _logger;

    public EmailSample (ILogger<EmailSample> logger)
    {
        _logger = logger;
    }
[Inject]
    public IMailService _mailService { get; set; }
    
    public void SendEmail()
    {
        string emailTo = "test@test.com";
        string emailFrom = "noreply@test.com";
        string emailSubject = "This is a test email.";
        string emailType = "html";         
        string emailCc = string.Empty;

        System.Text.StringBuilder sb = new System.Text.StringBuilder();
        sb.AppendLine("Hello" + " " + emailTo);
        sb.AppendLine("</br>");
        sb.AppendLine("This is a test of the email functionality");
        sb.AppendLine("</br>");
        sb.AppendLine("Best Regards,");
        sb.AppendLine("</br>");
        sb.AppendLine("Signature");
        string emailBody = sb.ToString();

        try
        {
            throw new Exception("This is an email sample exception test");
            //Task tSendEmail = _mailService.SendEmailAsync(emailTo, emailSubject, emailBody, emailFrom, emailCc, emailType);
            //if (tSendEmail.IsCompletedSuccessfully)
            //{
            //    _statusMessage = "The email has been sent successfully.";

            //}
            //else
            //{
            //    _statusMessage = "Failed to send email successfully.";
            //}
         
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "The email for { emailto } failed to send.", emailTo);
        }
    }
    public void OnGet()
    {

        _statusMessage = "";
    }
}

Answer 1

[Inject]
private ILogger<EmailSample> logger {get; set;}

不要忘记命名空间 Microsoft.Extensions.Logging

MissingMethodException：没有为类型定义无参数构造函数

MissingMethodException: No parameterless constructor defined for type

dependency-injection

serilog

blazor

microsoft.extensions.logging