我正在尝试解决其他问题。如果存储在string（id）中的字符不等于13，则程序必须显示“无效长度”，这些字符是在文本框import { Component, OnInit } from '@angular/core';
import * as _ from 'lodash';
@Component({
selector: 'app-hfo',
templateUrl: './hfo.component.html',
styleUrls: ['./hfo.component.css']
})
export class HfoComponent implements OnInit {
students: any;
filteredStudents: any;
// basic info
Sex: string;
// child info
ProgramCategory: string;
ProgramStatus: string;
// filter by value
filters = { };
constructor() { }
ngOnInit() {
/// get all students
this.students = this.getStudents();
this.setFilters();
}
private setFilters() {
this.filteredStudents = _.filter(this.students, _.conforms(this.filters) );
}
filterMatch(property: string, value: any) {
this.filters[property] = i => i === value;
this.setFilters();
}
filterMatchSub(property: string, childProperty: string, value: any) {
this.filters[property] = val => val.find( child => child[childProperty] === value);
this.setFilters();
}
/// removes filter
removeFilter(property: string) {
delete this.filters[property];
this[property] = null;
this.ProgramCategory = null;
this.ProgramStatus = null;
this.setFilters();
}
private getStudents() {
return JSON.parse(`
[
{
"StudentId": 1,
"StudentName": "Student1",
"Sex":"M",
"Programs": [
{
"StudentId": 1,
"ProgramName": "Java",
"ProgramCategory": "Engineering",
"ProgramStatus": "Full Time"
},
{
"StudentId": 1,
"ProgramName": "HR Management 2",
"ProgramCategory": "HR",
"ProgramStatus": "Part Time"
},
{
"StudentId": 1,
"ProgramName": "Accounting 1",
"ProgramCategory": "Finance",
"ProgramStatus": "Full Time"
}
]
},
{
"StudentId": 2,
"StudentName": "Student2",
"Sex":"F",
"Programs": [
{
"StudentId": 2,
"ProgramName": "HR Management 1",
"ProgramCategory": "HR",
"ProgramStatus": "Part Time"
},
{
"StudentId": 2,
"ProgramName": "Accounting 3",
"ProgramCategory": "Finance",
"ProgramStatus": "Full Time"
}
]
},
{
"StudentId": 3,
"StudentName": "Student3",
"Sex":"F",
"Programs": [
{
"StudentId": 3,
"ProgramName": "Java 3",
"ProgramCategory": "Engineering",
"ProgramStatus": "Full Time"
}
]
},
{
"StudentId": 4,
"StudentName": "Student4",
"Sex":"M",
"Programs": [
{
"StudentId": 4,
"ProgramName": "Java 2",
"ProgramCategory": "Engineering",
"ProgramStatus": "Full Time"
},
{
"StudentId": 4,
"ProgramName": "Accounting 2",
"ProgramCategory": "Finance",
"ProgramStatus": "Part Time"
}
]
},
{
"StudentId": 5,
"StudentName": "Student5",
"Sex":"M",
"Programs": [
{
"StudentId": 5,
"ProgramName": "JavaScript",
"ProgramCategory": "Engineering",
"ProgramStatus": "Part Time"
},
{
"StudentId": 5,
"ProgramName": "HR Management 5",
"ProgramCategory": "HR",
"ProgramStatus": "Full Time"
}
]
}
]
`);
}
}
中输入的。但是，只要满足此条件，我都会收到错误消息
System.ArgumentOutOfRangeException：'索引和长度必须引用字符串中的位置。参数名称：length'
<div class="row">
<div class="col-sm-12">
<div class="panel panel-sm ">
<div class="panel-body">
<h5>Basic Info</h5>
<div class="hs-lead">
<div class="row">
<div class="col-sm-3">
<div class="form-group">
<label for="exampleSelect1">Sex</label>
<div class="row">
<div class="col-sm-9">
<select class="form-control" [(ngModel)]="Sex" (change)="filterMatch('Sex', Sex)">
<option value="M">M</option>
<option value="F">F</option>
</select>
</div>
<div class="col-sm-3">
<button class="btn btn-primary" *ngIf="Sex" (click)="removeFilter('Sex')">
Clear
</button>
</div>
</div>
</div>
</div>
<div class="col-sm-3">
<div class="form-group">
<label for="exampleSelect1">ProgramCategory</label>
<div class="row">
<div class="col-sm-9">
<select class="form-control" [(ngModel)]="ProgramCategory" (change)="filterMatchSub('Programs', 'ProgramCategory', ProgramCategory)">
<option value="Engineering">Engineering</option>
<option value="HR">HR</option>
<option value="Finance">Finance</option>
</select>
</div>
<div class="col-sm-3">
<button class="btn btn-primary" *ngIf="ProgramCategory" (click)="removeFilter('Programs')">
Clear
</button>
</div>
</div>
</div>
</div>
<div class="col-sm-3">
<div class="form-group">
<label for="exampleSelect1">ProgramStatus</label>
<div class="row">
<div class="col-sm-9">
<select class="form-control" [(ngModel)]="ProgramStatus" (change)="filterMatchSub('Programs', 'ProgramStatus', ProgramStatus)">
<option value="Full Time">Full Time</option>
<option value="Part Time">Part Time</option>
</select>
</div>
<div class="col-sm-3">
<button class="btn btn-primary" *ngIf="ProgramStatus" (click)="removeFilter('Programs')">
Clear
</button>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
<div class="row">
<div class="col-sm-12">
<div class="panel panel-xl">
<div class="panel-body">
<h5>Result
<span class="badge badge-info badge-pill pull-right">{{ filteredStudents.length }}</span>
</h5>
<div class="hs-lead">
<div class="table-responsive">
<table class="table table-hover">
<thead>
<tr>
<th>#</th>
<th>Name</th>
<th>Sex</th>
<th>Programs</th>
</tr>
</thead>
<tbody>
<tr *ngFor="let item of filteredStudents ">
<td>{{item.StudentId }}</td>
<td>{{item.StudentName }}</td>
<td>{{item.Sex}}</td>
<td>
{{item.Programs.length}}
<ol *ngFor="let obj of item.Programs">
<li>{{obj.ProgramCategory}} / {{obj.ProgramStatus}}</li>
</ol>
</td>
</tr>
</tbody>
</table>
</div>
</div>
</div>
</div>
</div>
</div>
答案 0 :(得分：1)
.Substring()将引发异常，如果您尝试超出其范围。因此，如果单词“ josh”而您去了"josh".Substring(0,8)，则它将抛出异常，因为josh只有4个字母，而我试图将其子字符串化为8。
要解决此问题，请先检查长度
if (!(txtId.Text.Length==13))
{
LblDisp.Text = "Invalid Length";
}
else
{
string id = txtId.Text; // you do not need to even do SubString now as you know it is a length of 13
string year = id.Substring(0, 2).ToString();
string month = id.Substring(2, 2).ToString();
string day = id.Substring(4, 2).ToString();
string gender = id.Substring(6, 1).ToString();
int yy = int.Parse(year);
int mm = int.Parse(month);
int dd = int.Parse(day);
int xx = int.Parse(gender);
if (!(yy >= 40 && yy <= 99) || (yy >=0 && yy <= 18))
{
LblDisp.Text = "Invalid Year";
}
答案 1 :(得分：1)
您要尝试的是称为guard cause的模式。
// check for the length first
if (txtId.Text.Length < 13)
{
LblDisp.Text = "Invalid Length";
return;
}
// use substring later. You dont want to substring on a short string.
// If you try you can get ArgumentOutOfRangeException.
string id = txtId.Text;
string year = id.Substring(0, 2); // substring returns a string
string month = id.Substring(2, 2);
string day = id.Substring(4, 2);
string gender = id.Substring(6, 1);
// by the way, you should check if all this chars are numbers. You can use int.TryParse for this.
int yy = int.TryParse(year);
int mm = int.Parse(month);
int dd = int.Parse(day);
int xx = int.Parse(gender);
if (!(yy >= 40 && yy <= 99) || (yy >=0 && yy <= 18))
{
LblDisp.Text = "Invalid Year";
}
答案 2 :(得分：0)
.Substring()将失败并显示该错误。
即如果字符串少于13个字符，而您尝试采用13个字符的子字符串，则会出现该错误。