如何在C＃中验证数字的输入项是否不带有“ 0”

Question

我有一个类型为import React from "react"; import Highcharts from "highcharts"; import HC_exporting from "highcharts/modules/exporting"; import HC_exporting_data from "highcharts/modules/export-data"; import PropTypes from "prop-types"; class HCLineChart extends React.Component { constructor(props){ super(props); HC_exporting(Highcharts); HC_exporting_data(Highcharts); } componentDidMount() { this.highChartsRender(this.props.options); } shouldComponentUpdate(nextProps) { this.highChartsRender(nextProps.options); return false; } highChartsRender(options) { Highcharts.chart(this.props.id,{ chart: { type: "line", renderTo: "lineChart", height: 500, }, title: { text: this.props.title, }, xAxis: { categories: options.xAxisCategories, }, yAxis: { title: { text: this.props.title, }, }, plotOptions: { series: { marker: { enabled: false, }, }, }, credits:{ enabled: false, }, exporting: { buttons: { contextButton: { enabled: true, menuItems: [ "printChart", "downloadCSV", "downloadXLS", ], }, }, }, series: options.data, }); Highcharts.setOptions({ lang: { thousandsSep: ",", }, }); } render() { return <div className="line-chart" id={this.props.id} />; } } export default HCLineChart; 的控件，我不想让用户输入以“ 0”开头的值，例如...

  

0

     

01

     

00

     

00010

但是如果我想输入自然数形式的包含“ 0”的值，例如...

  

10

     

2010

     

200000

<Entry>：

MyView.XAML

<Entry HorizontalOptions="FillAndExpand" Placeholder="Cantidad" Keyboard="Numeric" MaxLength="9" Text="{Binding CantidadContenedor}"></Entry> ：

MyViewModel.CS

捕获 string cantidadContenedor; public string CantidadContenedor { get { return cantidadContenedor; } set { if (cantidadContenedor != value) { cantidadContenedor = value; PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(CantidadContenedor))); } } } 的值后如何添加此验证？

我可以占用Entry类型为TryParse的{​​{1}}属性吗？

对我有帮助吗？

Answer 1

这个工作完美！

    public MainPage()
    {
        InitializeComponent();

        MyEntry.TextChanged+= MyEntry_TextChanged;
    }

    void MyEntry_TextChanged(object sender, Xamarin.Forms.TextChangedEventArgs e)
    {
        if(!string.IsNullOrWhiteSpace(MyEntry.Text))
        {
            if (MyEntry.Text.StartsWith("0"))
                MyEntry.Text = e.OldTextValue;
        }
    }

Answer 2

您可以转换任何以string的价格接收的值。

然后只需将第一个数字作为子字符串读取，如下所示：

using System;

public class Program
{
    public static void Main()
    {
        string x = "0TEST";
        if(x.StartsWith("0")){
            Console.WriteLine("Starts with 0");
        }else{
            Console.WriteLine("Doesn't start with 0");
        }
    }
}

然后写逻辑以允许/拒绝它。

Answer 3

我将创建一个验证规则。

在您的XAML中

<Entry
  HorizontalOptions="FillAndExpand"
  Placeholder="Cantidad"
  Keyboard="Numeric"
  MaxLength="9">
  <Entry.Text>
     <Binding Path=CantidadContenedor>
         <Binding.ValidationRules>
             <validationRules:StartWithRule Prefix="0"/>
     </Binding>
  </Entry.Text>
</Entry>

现在，您可以创建自己认为合适的验证了。就您而言

public class StartWithRule : ValidationRule
{
    public string Prefix { get; set; }

    public override ValidationResult Validate(object value, CultureInfo cultureInfo)
    {
        // Pass the value to string
        var numberToCheck = (string) value;

        if (numberToCheck == null) return ValidationResult.ValidResult;

        // Check if it starts with prefix
        return numberToCheck.StartsWith(Prefix)
            ? new ValidationResult(false, $"Starts with {Prefix}")
            : ValidationResult.ValidResult;
    }
}

您应该很好。