如何重置选择默认值Angular2

<select class="form-control" aria-placeholder="Select File" style=" margin-right:5px;padding:0px;width:400px" [(ngModel)]="ddlFileId" (change)="loadFiles($event.target.value)"  [ngModelOptions]="{standalone: true}" >
    <option [value]="''" disabled selected>Select File</option> // this will appear like a place holder
    <option *ngFor="let file of AllFileIDS" [value]="file.FileID" [ngValue]="file.FileID">{{file.FileID}}</option>
</select>

this.ddlFileId = "";

我不确定你是如何重置你的表单的,但我也很难将重置选择回到Angular 2中的默认值.但是我已经使用了一些自定义的值设置.在我的场景中,我使用0作为我的选择的默认值,但我尝试”它也可以.我用下面的空字符串默认换出了我的0默认值.请注意,我没有使用绑定[value],只是使用常规值而只使用单引号,而不是使用双引号.

<select id="selectSchool" [disabled]="user.roleId>2" class="form-control" [(ngModel)]="model.schoolId" name="schoolid" required (ngModelChange)="onSchoolChange($event)">
    <!--<option value="0" selected>Select School</option>-->
    <option value='' disabled selected>Select File</option>
    <option value="{{school.id}}" *ngFor="let school of schools">{{school.name}}</option>
</select>

我使用ViewChild将表单拉入我的component.ts文件：

import { ViewChild,Component,OnInit } from '@angular/core';

将表单设置为组件中的变量：

export class UserComponent {
    @ViewChild("f")
    f: NgForm;

HTML模板中的表单标记如下所示：

<form name="form" class="form-horizontal" (ngSubmit)="f.form.valid && submit()" #f="ngForm" novalidate>

我的提交功能在提交后清除表单

submit(): void {
    // my submit code....

    // reset form
    this.f.resetForm();

    // After the reset,the selects will be cleared to nulls
    // even setting the model values back to '' or 0 does not rebind them. (seems like a bug)
    // but setting the form values back manually works.
    this.f.form.controls.schoolid.setValue('');  // <--- Here is resetting a select back to a default '' value
    this.f.form.controls.active.setValue(true);
    this.f.form.controls.roleid.setValue(0);  // <-- Here is resetting a select back to a default 0 value
    this.f.form.controls.radioGender.setValue("M");
}