CORS 策略阻止了从来源 'http://localhost:3000' 在 'https://localhost:7144/api/employees' 获取的访问权限

Question

当我尝试从 webapi 获取数据以在 React js 中显示时出现此错误 Here is a photo when I check the console this is what I get

这是我的 program.cs

using WebApp.Data;

var myAllowSpecificOrigins = "_myAllowSpecificOrigins";

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.

builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

builder.Services.AddDbContext<DataContext>(options =>
{
    options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection"));
});

//Enable CORS
builder.Services.AddCors(options =>
{
    options.AddPolicy(name: myAllowSpecificOrigins,
        builder =>
        {
            builder.WithOrigins("http://localhost:3000/")
            .AllowAnyMethod()
            .AllowAnyHeader();
        });
});

var app = builder.Build();
// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();

app.UseCors(myAllowSpecificOrigins);

app.UseAuthorization();

app.MapControllers();

app.Run();

这是我的一个文件employee.js

import {variables} from './variables.js';

export class Employee extends Component{

    constructor(props){
        super(props);

        this.state={
            departments:[],
            employees:[],
            modalTitle:"",
            EmployeeId:0,
            EmployeeName:"",
            Department:"",
            DateOfJoining:"",

        }
    }

    refreshList(){

        fetch(variables.API_URL+'employees')
        .then(response=>response.json())
        .then(data=>{
            this.setState({employees:data});
        });

        fetch(variables.API_URL+'department')
        .then(response=>response.json())
        .then(data=>{
            this.setState({departments:data});
        });
    }

    componentDidMount(){
        this.refreshList();
    }
    
    changeEmployeeName =(e)=>{
        this.setState({EmployeeName:e.target.value});
    }
    changeDepartment =(e)=>{
        this.setState({Department:e.target.value});
    }
    changeDateOfJoining =(e)=>{
        this.setState({DateOfJoining:e.target.value});
    }

    addClick(){
        this.setState({
            modalTitle:"Add Employee",
            EmployeeId:0,
            EmployeeName:"",
            Department:"",
            DateOfJoining:"",
            PhotoFileName:"anonymous.png"
        });
    }
    editClick(emp){
        this.setState({
            modalTitle:"Edit Employee",
            EmployeeId:emp.EmployeeId,
            EmployeeName:emp.EmployeeName,
            Department:emp.Department,
            DateOfJoining:emp.DateOfJoining,
            PhotoFileName:emp.PhotoFileName
        });
    }

    createClick(){
        fetch(variables.API_URL+'employee',{
            method:'POST',
            headers:{
                'Accept':'application/json',
                'Content-Type':'application/json'
            },
            body:JSON.stringify({
                EmployeeName:this.state.EmployeeName,
                Department:this.state.Department,
                DateOfJoining:this.state.DateOfJoining,
                PhotoFileName:this.state.PhotoFileName
            })
        })
        .then(res=>res.json())
        .then((result)=>{
            alert(result);
            this.refreshList();
        },(error)=>{
            alert('Failed');
        })
    }


    updateClick(){
        fetch(variables.API_URL+'employee',{
            method:'PUT',
            headers:{
                'Accept':'application/json',
                'Content-Type':'application/json'
            },
            body:JSON.stringify({
                EmployeeId:this.state.EmployeeId,
                EmployeeName:this.state.EmployeeName,
                Department:this.state.Department,
                DateOfJoining:this.state.DateOfJoining,
                PhotoFileName:this.state.PhotoFileName
            })
        })
        .then(res=>res.json())
        .then((result)=>{
            alert(result);
            this.refreshList();
        },(error)=>{
            alert('Failed');
        })
    }

    deleteClick(id){
        if(window.confirm('Are you sure?')){
        fetch(variables.API_URL+'employee/'+id,{
            method:'DELETE',
            headers:{
                'Accept':'application/json',
                'Content-Type':'application/json'
            }
        })
        .then(res=>res.json())
        .then((result)=>{
            alert(result);
            this.refreshList();
        },(error)=>{
            alert('Failed');
        })
        }
    }

    imageUpload=(e)=>{
        e.preventDefault();

        const formData=new FormData();
        formData.append("file",e.target.files[0],e.target.files[0].name);

        fetch(variables.API_URL+'employee/savefile',{
            method:'POST',
            body:formData
        })
        .then(res=>res.json())
        .then(data=>{
            this.setState({PhotoFileName:data});
        })
    }

    render(){
        const {
            departments,
            employees,
            modalTitle,
            EmployeeId,
            EmployeeName,
            Department,
            DateOfJoining,
            PhotoPath,
            PhotoFileName
        }=this.state;

        return(
<div>

    <button type="button"
    className="btn btn-primary m-2 float-end"
    data-bs-toggle="modal"
    data-bs-target="#exampleModal"
    onClick={()=>this.addClick()}>
        Add Employee
    </button>
    <table className="table table-striped">
    <thead>
    <tr>
        <th>
            EmployeeId
        </th>
        <th>
            EmployeeName
        </th>
        <th>
            Department
        </th>
        <th>
            DOJ
        </th>
        <th>
            Options
        </th>
    </tr>
    </thead>
    <tbody>
        {employees.map(emp=>
            <tr key={emp.EmployeeId}>
                <td>{emp.EmployeeId}</td>
                <td>{emp.EmployeeName}</td>
                <td>{emp.Department}</td>
                <td>{emp.DateOfJoining}</td>
                <td>
                <button type="button"
                className="btn btn-light mr-1"
                data-bs-toggle="modal"
                data-bs-target="#exampleModal"
                onClick={()=>this.editClick(emp)}>
                    <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" className="bi bi-pencil-square" viewBox="0 0 16 16">
                    <path d="M15.502 1.94a.5.5 0 0 1 0 .706L14.459 3.69l-2-2L13.502.646a.5.5 0 0 1 .707 0l1.293 1.293zm-1.75 2.456-2-2L4.939 9.21a.5.5 0 0 0-.121.196l-.805 2.414a.25.25 0 0 0 .316.316l2.414-.805a.5.5 0 0 0 .196-.12l6.813-6.814z"/>
                    <path fillRule="evenodd" d="M1 13.5A1.5 1.5 0 0 0 2.5 15h11a1.5 1.5 0 0 0 1.5-1.5v-6a.5.5 0 0 0-1 0v6a.5.5 0 0 1-.5.5h-11a.5.5 0 0 1-.5-.5v-11a.5.5 0 0 1 .5-.5H9a.5.5 0 0 0 0-1H2.5A1.5 1.5 0 0 0 1 2.5v11z"/>
                    </svg>
                </button>

                <button type="button"
                className="btn btn-light mr-1"
                onClick={()=>this.deleteClick(emp.EmployeeId)}>
                    <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" className="bi bi-trash-fill" viewBox="0 0 16 16">
                    <path d="M2.5 1a1 1 0 0 0-1 1v1a1 1 0 0 0 1 1H3v9a2 2 0 0 0 2 2h6a2 2 0 0 0 2-2V4h.5a1 1 0 0 0 1-1V2a1 1 0 0 0-1-1H10a1 1 0 0 0-1-1H7a1 1 0 0 0-1 1H2.5zm3 4a.5.5 0 0 1 .5.5v7a.5.5 0 0 1-1 0v-7a.5.5 0 0 1 .5-.5zM8 5a.5.5 0 0 1 .5.5v7a.5.5 0 0 1-1 0v-7A.5.5 0 0 1 8 5zm3 .5v7a.5.5 0 0 1-1 0v-7a.5.5 0 0 1 1 0z"/>
                    </svg>
                </button>

                </td>
            </tr>
            )}
    </tbody>
    </table>

<div className="modal fade" id="exampleModal" tabIndex="-1" aria-hidden="true">
<div className="modal-dialog modal-lg modal-dialog-centered">
<div className="modal-content">
   <div className="modal-header">
       <h5 className="modal-title">{modalTitle}</h5>
       <button type="button" className="btn-close" data-bs-dismiss="modal" aria-label="Close"
       ></button>
   </div>

   <div className="modal-body">
    <div className="d-flex flex-row bd-highlight mb-3">
     
     <div className="p-2 w-50 bd-highlight">
    
        <div className="input-group mb-3">
            <span className="input-group-text">Emp Name</span>
            <input type="text" className="form-control"
            value={EmployeeName}
            onChange={this.changeEmployeeName}/>
        </div>

        <div className="input-group mb-3">
            <span className="input-group-text">Department</span>
            <select className="form-select"
            onChange={this.changeDepartment}
            value={Department}>
                {departments.map(dep=><option key={dep.DepartmentId}>
                    {dep.DepartmentName}
                </option>)}
            </select>
        </div>

        <div className="input-group mb-3">
            <span className="input-group-text">DOJ</span>
            <input type="date" className="form-control"
            value={DateOfJoining}
            onChange={this.changeDateOfJoining}/>
        </div>


     </div>
     <div className="p-2 w-50 bd-highlight">
         <img width="250px" height="250px"
         src={PhotoPath+PhotoFileName}/>
         <input className="m-2" type="file" onChange={this.imageUpload}/>
     </div>
    </div>

    {EmployeeId==0?
        <button type="button"
        className="btn btn-primary float-start"
        onClick={()=>this.createClick()}
        >Create</button>
        :null}

        {EmployeeId!=0?
        <button type="button"
        className="btn btn-primary float-start"
        onClick={()=>this.updateClick()}
        >Update</button>
        :null}
   </div>

</div>
</div> 
</div>


</div>
        )
    }
}

我认为这个问题必须处理 CORS 策略，但已尝试了所有方法。有什么对任何人来说都很突出吗？我应该怎么做才能防止这种情况并显示来自 webapi 的数据以做出反应？

Answer 1

你必须删除尾随的“/”，应该是

 builder.WithOrigins("http://localhost:3000")

CORS 策略阻止了从来源 'http://localhost:3000' 在 'https://localhost:7144/api/employees' 获取的访问权限

Access to fetch at 'https://localhost:7144/api/employees' from origin 'http://localhost:3000' has been blocked by CORS policy

.net

javascript

c#

asp.net-web-api

reactjs