在Angular NGRX中，要根据id选择ngrx entity中的单个值，你可以使用selectEntityById选择器。以下是一个示例：

1. 在你的状态文件中，定义一个entityAdapter和一个entityState：

import { createEntityAdapter, EntityState } from '@ngrx/entity';

export interface User {
  id: number;
  name: string;
}

export const userAdapter = createEntityAdapter();

export interface UserState extends EntityState {
  selectedUserId: number | null;
}

export const initialState: UserState = userAdapter.getInitialState({
  selectedUserId: null
});

2. 创建一个users.reducer.ts文件，并使用createReducer来创建一个reducer函数：

import { createReducer, on } from '@ngrx/store';
import { EntityState, createEntityAdapter } from '@ngrx/entity';
import { selectUser } from './users.actions';

export interface User {
  id: number;
  name: string;
}

export const userAdapter = createEntityAdapter();

export interface UserState extends EntityState {
  selectedUserId: number | null;
}

export const initialState: UserState = userAdapter.getInitialState({
  selectedUserId: null
});

export const userReducer = createReducer(
  initialState,
  on(selectUser, (state, { id }) => ({
    ...state,
    selectedUserId: id
  }))
);

3. 创建一个users.selectors.ts文件，并使用createFeatureSelector和selectEntityById来创建一个选择器：

import { createSelector, createFeatureSelector } from '@ngrx/store';
import { UserState, userAdapter } from './users.reducer';

export const selectUserState = createFeatureSelector('users');

export const {
  selectIds,
  selectEntities,
  selectAll,
  selectTotal,
} = userAdapter.getSelectors(selectUserState);

export const selectSelectedUserId = createSelector(
  selectUserState,
  (state) => state.selectedUserId
);

export const selectSelectedUser = createSelector(
  selectEntities,
  selectSelectedUserId,
  (entities, selectedUserId) => entities[selectedUserId]
);

4. 在你的组件中使用selectSelectedUser选择器来获取所选用户的单个值：

import { Component, OnInit } from '@angular/core';
import { Store } from '@ngrx/store';
import { Observable } from 'rxjs';
import { User } from './users.reducer';
import { selectSelectedUser } from './users.selectors';

@Component({
  selector: 'app-user-detail',
  template: `
    

      
User Details
      
Name: {{ user.name }}
    
  `,
})
export class UserDetailComponent implements OnInit {
  user$: Observable;

  constructor(private store: Store) {}

  ngOnInit() {
    this.user$ = this.store.select(selectSelectedUser);
  }
}

现在，当你选择一个用户时，UserDetailComponent组件将根据所选用户的id显示用户的详细信息。

以上就是使用selectEntityById选择器来根据id选择ngrx entity中的单个值的解决方法。