要在Angular 10中使用'oidc-client'与IdentityServer4 .Net Core 3.1，可以按照以下步骤进行设置：

1. 在Angular项目中安装'oidc-client'库：

npm install oidc-client --save

2. 创建一个名为auth.service.ts的Angular服务文件，并添加以下代码：

import { Injectable } from '@angular/core';
import { UserManager, User } from 'oidc-client';

@Injectable({
  providedIn: 'root'
})
export class AuthService {
  private userManager: UserManager;

  constructor() {
    const config = {
      authority: 'https://identityserver.example.com',
      client_id: 'your_client_id',
      redirect_uri: 'http://localhost:4200/callback',
      response_type: 'code',
      scope: 'openid profile',
      post_logout_redirect_uri: 'http://localhost:4200',
    };

    this.userManager = new UserManager(config);
  }

  login(): void {
    this.userManager.signinRedirect();
  }

  logout(): void {
    this.userManager.signoutRedirect();
  }

  completeAuthentication(): Promise {
    return this.userManager.signinRedirectCallback();
  }

  getUser(): Promise {
    return this.userManager.getUser();
  }
}

3. 在app.module.ts中将AuthService添加到providers数组中：

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';

import { AppComponent } from './app.component';
import { AuthService } from './auth.service';

@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule
  ],
  providers: [AuthService],
  bootstrap: [AppComponent]
})
export class AppModule { }

4. 在app.component.ts中使用AuthService：

import { Component, OnInit } from '@angular/core';
import { AuthService } from './auth.service';

@Component({
  selector: 'app-root',
  template: `
    Login
    Logout
    

      
Welcome, {{ userName }}
    
  `
})
export class AppComponent implements OnInit {
  isLoggedIn = false;
  userName = '';

  constructor(private authService: AuthService) {}

  ngOnInit(): void {
    this.authService.completeAuthentication().then(user => {
      if (user && user.access_token) {
        this.isLoggedIn = true;
        this.userName = user.profile.name;
      }
    });
  }

  login(): void {
    this.authService.login();
  }

  logout(): void {
    this.authService.logout();
    this.isLoggedIn = false;
    this.userName = '';
  }
}

上述代码中的配置信息需要替换为你的IdentityServer4实例的相关信息，包括authority、client_id、redirect_uri和scope等。

使用上述代码，你可以在Angular应用程序中实现OpenID Connect身份验证和授权。