找不到Http发布端点

Question

我有以下反应代码来调用webapi发布端点。

import React, { Component } from 'react';
import { Input} from 'antd';
import Form from '../../components/uielements/form';
import Button from '../../components/uielements/button';
import Notification from '../../components/notification';
import { adalApiFetch } from '../../adalConfig';


const FormItem = Form.Item;

class CreateSiteCollectionForm extends Component {
    constructor(props) {
        super(props);
        this.state = {Alias:'',DisplayName:'', Description:''};
        this.handleChangeAlias = this.handleChangeAlias.bind(this);
        this.handleChangeDisplayName = this.handleChangeDisplayName.bind(this);
        this.handleChangeDescription = this.handleChangeDescription.bind(this);
        this.handleSubmit = this.handleSubmit.bind(this);
    };

    handleChangeAlias(event){
        this.setState({Alias: event.target.value});
    }

    handleChangeDisplayName(event){
        this.setState({DisplayName: event.target.value});
    }

    handleChangeDescription(event){
        this.setState({Description: event.target.value});
    }

    handleSubmit(e){
        e.preventDefault();
        this.props.form.validateFieldsAndScroll((err, values) => {
            if (!err) {
                let data = new FormData();
                //Append files to form data
                //data.append(

                const options = {
                  method: 'post',
                  body: JSON.stringify(
                    {
                        "Alias": this.state.Alias,
                        "DisplayName": this.state.DisplayName, 
                        "Description": this.state.Description
                    }),
                  config: {
                    headers: {
                      'Content-Type': 'multipart/form-data'
                    }
                  }
                };

                adalApiFetch(fetch, "/SiteCollections/CreateModernSite", options)
                  .then(response =>{
                    if(response.status === 204){
                        Notification(
                            'success',
                            'Site collection created',
                            ''
                            );
                     }else{
                        throw "error";
                     }
                  })
                  .catch(error => {
                    Notification(
                        'error',
                        'Site collection not created',
                        error
                        );
                    console.error(error);
                });
            }
        });      
    }

    render() {
        const { getFieldDecorator } = this.props.form;
        const formItemLayout = {
        labelCol: {
            xs: { span: 24 },
            sm: { span: 6 },
        },
        wrapperCol: {
            xs: { span: 24 },
            sm: { span: 14 },
        },
        };
        const tailFormItemLayout = {
        wrapperCol: {
            xs: {
            span: 24,
            offset: 0,
            },
            sm: {
            span: 14,
            offset: 6,
            },
        },
        };
        return (
            <Form onSubmit={this.handleSubmit}>
                <FormItem {...formItemLayout} label="Alias" hasFeedback>
                {getFieldDecorator('Alias', {
                    rules: [
                        {
                            required: true,
                            message: 'Please input your alias',
                        }
                    ]
                })(<Input name="alias" id="alias" onChange={this.handleChangeAlias} />)}
                </FormItem>
                <FormItem {...formItemLayout} label="Display Name" hasFeedback>
                {getFieldDecorator('displayname', {
                    rules: [
                        {
                            required: true,
                            message: 'Please input your display name',
                        }
                    ]
                })(<Input name="displayname" id="displayname" onChange={this.handleChangedisplayname} />)}
                </FormItem>
                <FormItem {...formItemLayout} label="Description" hasFeedback>
                {getFieldDecorator('description', {
                    rules: [
                        {
                            required: true,
                            message: 'Please input your description',
                        }
                    ],
                })(<Input name="description" id="description"  onChange={this.handleChangeDescription} />)}
                </FormItem>

                <FormItem {...tailFormItemLayout}>
                    <Button type="primary" htmlType="submit">
                        Create modern site
                    </Button>
                </FormItem>
            </Form>
        );
    }
}

const WrappedCreateSiteCollectionForm = Form.create()(CreateSiteCollectionForm);
export default WrappedCreateSiteCollectionForm;

但是我没有找到404：

这是我的webapi代码。

 [HttpPost]
        [Route("api/SiteCollections/CreateModernSite")]
        public async Task<string>  CreateModernSite(string Alias, string DisplayName, string Description)
        {
            var tenant = await TenantHelper.GetTenantAsync();
            using (var context = new OfficeDevPnP.Core.AuthenticationManager().GetAppOnlyAuthenticatedContext(tenant.TenantAdminUrl, tenant.ClientId, tenant.ClientSecret))
            {
                 var teamContext = await context.CreateSiteAsync(
                    new TeamSiteCollectionCreationInformation
                    {
                        Alias = Alias, // Mandatory
                        DisplayName = DisplayName, // Mandatory
                        Description = Description, // Optional
                        //Classification = Classification, // Optional
                        //IsPublic = IsPublic, // Optional, default true
                    }
                );
                teamContext.Load(teamContext.Web, w => w.Url);
                teamContext.ExecuteQueryRetry();
                return teamContext.Web.Url;
            }
        }