ManagementObjectSearcher query = new ManagementObjectSearcher(
     "select Name,CurrentClockSpeed from Win32_Processor");

ManagementObjectCollection queryCollection = query.Get();

ManagementObject mo = queryCollection[0];

但是因为它支持IEnumerable,所以你可以使用Linq：

ManagementObject mo = queryCollection.OfType<ManagementObject>().FirstOrDefault()

OfType<&的ManagementObject GT;是必需的,因为ManagementObjectCollection支持IEnumerable但不支持IEnumerable of T.

Can’t resolve all parameters for AuthenticationService: ([object Object],?,[object Object])

我已经检查了几乎每个主题,并尝试了多种方法来解决它,但仍然无法在第二天击败它.

我试图像这样在appService中注入第一个authService但是得到了同样的错误

@Inject(forwardRef(() => AuthenticationService)) public authService: AuthenticationService

我检查了所有DI和服务内部的导入顺序,在我看来一切都是正确的

如果有人可以帮我处理它,我很感激.

Angular 4.0.0

AuthService

import { Injectable } from '@angular/core';
import {Http,Headers,Response} from '@angular/http';
import 'rxjs/add/operator/toPromise';
import {Observable} from 'rxjs/Rx';

import {AppServices} from "../../app.services";
import {Router} from "@angular/router";

@Injectable()
export class AuthenticationService {
  public token: any;

  constructor(
    private http: Http,private appService: AppServices,private router: Router
  ) {
    this.token = localStorage.getItem('token');
  }

  login(username: string,password: string): Observable<boolean> {
    let headers = new Headers();
    let body = null;
    headers.append("Authorization",("Basic " + btoa(username + ':' + password)));

    return this.http.post(this.appService.api + '/login',body,{headers: headers})
      .map((response: Response) => {
        let token = response.json() && response.json().token;
        if (token) {
          this.token = token;
          localStorage.setItem('Conform_token',token);
          return true;
        } else {
          return false;
        }
      });
  }

  logout(): void {
    this.token = null;
    localStorage.removeItem('Conform_token');
    this.router.navigate(['/login']);
  }
}

应用服务

import {Injectable} from '@angular/core';
import {Headers,Http,RequestOptions} from '@angular/http';
import {Router} from "@angular/router";
import {AuthenticationService} from "./auth/auth.service";

import 'rxjs/add/operator/toPromise';
import {Observable} from 'rxjs/Rx';

@Injectable()

export class AppServices {

  api = '//endpoint/';

  public options: any;
  constructor(
    private http: Http,private router: Router,public authService: AuthenticationService // doesn't work
  //  @Inject(forwardRef(() => AuthenticationService)) public authService: AuthenticationService // doesn't work either
      ) {
        let head = new Headers({
      'Authorization': 'Bearer ' + this.authService.token,"Content-Type": "application/json; charset=utf8"
    });
    this.options = new RequestOptions({headers: head});
  }

  // ====================
  //    data services
  // ====================

  getData(): Promise<any> {
    return this.http
      .get(this.api + "/data",this.options)
      .toPromise()
      .then(response => response.json() as Array<Object>)
      .catch((err)=>{this.handleError(err);})
  }

应用模块

import { browserModule } from '@angular/platform-browser';
import { browserAnimationsModule } from '@angular/platform-browser/animations';

import { NgModule } from '@angular/core';
import { FormsModule } from '@angular/forms';
import {BaseRequestOptions,HttpModule} from '@angular/http';

import { MaterialModule} from '@angular/material';
import {FlexLayoutModule} from "@angular/flex-layout";
import 'hammerjs';

import { routing,appRoutingProviders }  from './app.routing';
import { AppServices } from './app.services';
import {AuthGuard} from "./auth/auth.guard";
import {AuthenticationService} from "./auth/auth.service";

import {AppComponent} from './app.component';
import {AuthComponent} from './auth/auth.component';
import {NotFoundComponent} from './404/not-found.component';
import { HomeComponent } from './home/home.component';

@NgModule({
  declarations: [
    AppComponent,AuthComponent,NotFoundComponent,HomeComponent
  ],imports: [
    browserModule,browserAnimationsModule,FormsModule,HttpModule,routing,MaterialModule,FlexLayoutModule
  ],providers: [AppServices,AuthGuard,AuthenticationService],bootstrap: [AppComponent]
})
export class AppModule { }

你可以使用

export class AuthenticationService {
  public token: any;
  appService: AppServices;
  constructor(
    private http: Http,// private appService: AppServices,injector:Injector;
    private router: Router
  ) {
    setTimeout(() => this.appService = injector.get(AppServices));
    this.token = localStorage.getItem('token');
  }

另见DI with cyclic dependency with custom HTTP and ConfigService

要避免使用setTimeout,您还可以从AppService的构造函数中设置AuthenticationService.appService(或者相反)

int apId = Convert.ToInt32(Request.QueryString["ApplicationID"]);

            ApplicationBLL objGetApplication = new ApplicationBLL();

            Appdec.YEP.BusinessEntities.Application objApplication =
            objGetApplication.GetApplicationByApplicationID(apId);



            objApplication.Status = (ddlStatus.SelectedValue == "0" ? false : true);



            new ApplicationBLL(new Appdec.YEP.DataAccessLayer.DatabaseContext()).UpdateApplication(objApplication);

现在商务逻辑的更新方法是

[System.ComponentModel.DataObjectMethodAttribute(System.ComponentModel.DataObjectMethodType.Update,true)]
    public void UpdateApplication(Application updatedApplication)
    {
        // Validate Parameters
        if (updatedApplication == null)
            throw (new ArgumentNullException("updatedApplication"));

        // Validate Primary key value
        if (updatedApplication.ApplicationID.IsInvalidKey())
            BusinessLayerHelper.ThrowErrorForInvalidDataKey("ApplicationID");

        // Apply business rules
        OnApplicationSaving(updatedApplication);
        OnApplicationUpdating(updatedApplication);

        //attaching and making ready for parsistance
        if (updatedApplication.EntityState == EntityState.Detached)
            _DatabaseContext.Applications.Attach(updatedApplication);



_DatabaseContext.ObjectStateManager.ChangeObjectState(updatedApplication,System.Data.EntityState.Modified);//this line throws the error 
//ObjectStateManager does not contain an ObjectStateEntry with a reference to an object of type
        int numberOfAffectedRows = _DatabaseContext.SaveChanges();
        if (numberOfAffectedRows == 0) 
            throw new DatanotUpdatedException("No application updated!");

        //Apply business workflow
        OnApplicationUpdated(updatedApplication);
        OnApplicationSaved(updatedApplication);

    }

有人可以告诉我如何修复此错误并更新表.
当我尝试更新其他表时,同样的错误发生.插件工作正常.
希望不要打扰你.最好的祝福.

也改变

if (newApp .EntityState == EntityState.Detached)
            _DatabaseContext.Applications.Attach(newApp );

至

var newApp = Application ();
 //copy all propery of updatedApplication to  newApp here 

            if (newApp .EntityKey == null || newApp .EntityKey.Istemporary)
            {
                _DatabaseContext.Applications.Addobject(newApp );
            }
            else
            {
                _DatabaseContext.Applications.Attach(newApp );
            }
_DatabaseContext.ObjectStateManager.ChangeObjectState(newApp,System.Data.EntityState.Modified);