一、前言

WPF没有内置IP地址输入控件，因此我们需要通过自己定义实现。

我们先看一下IP地址输入控件有什么特性：

输满三个数字焦点会往右移  键盘←→可以空光标移动  任意位置可复制整段IP地址，且支持x.x.x.x格式的粘贴赋值  删除字符会自动向左移动焦点

知道以上特性，我们就可以开始动手了。

二、构成

Grid+TextBox*4+TextBlock*3

通过这几个控件的组合，我们完成IP地址输入控件的功能。

界面代码如下：

三、验证输入格式

界面中为TextBox添加了CustomTextBoxTextStyle及validationTemplate样式，当输入格式不正确时，控件就会应用该样式。

通过自定义规则IPRangeValidationRule来验证输入的内容格式是否要求。

自定义规则代码如下：

public class IPRangeValidationRule : ValidationRule{ private int _min; private int _max; public int Min {  get { return _min; }  set { _min = value; } } public int Max {  get { return _max; }  set { _max = value; } } public override ValidationResult Validate(object value, CultureInfo cultureInfo) {  int val = 0;  var strVal = (string)value;  try  {   if (strVal.Length > 0)   {    if (strVal.EndsWith("."))    {     return CheckRanges(strVal.Replace(".", ""));    }    // Allow dot character to move to next box    return CheckRanges(strVal);   }  }  catch (Exception e)  {   return new ValidationResult(false, "Illegal characters or " + e.Message);  }  if ((val < Min) || (val > Max))  {   return new ValidationResult(false,    "Please enter the value in the range: " + Min + " - " + Max + ".");  }  else  {   return ValidationResult.ValidResult;  } } private ValidationResult CheckRanges(string strVal) {  if (int.TryParse(strVal, out var res))  {   if ((res < Min) || (res > Max))   {    return new ValidationResult(false,     "Please enter the value in the range: " + Min + " - " + Max + ".");   }   else   {    return ValidationResult.ValidResult;   }  }  else  {   return new ValidationResult(false, "Illegal characters entered");  } }}

四、控制焦点变化

在界面代码中我通过local:FocusChangeExtension.IsFocused附加属性实现绑定属性控制焦点的变化。

附加属性的代码如下：

public static class FocusChangeExtension{ public static bool GetIsFocused(DependencyObject obj) {  return (bool)obj.GetValue(IsFocusedProperty); } public static void SetIsFocused(DependencyObject obj, bool value) {  obj.SetValue(IsFocusedProperty, value); } public static readonly DependencyProperty IsFocusedProperty =  DependencyProperty.RegisterAttached(   "IsFocused", typeof(bool), typeof(FocusChangeExtension),   new UIPropertyMetadata(false, OnIsFocusedPropertyChanged)); private static void OnIsFocusedPropertyChanged(  DependencyObject d,  DependencyPropertyChangedEventArgs e) {  var control = (UIElement)d;  if ((bool)e.NewValue)  {   control.Focus();  } }}

五、VM+后台代码混合实现焦点控制及内容复制粘贴

1、后台代码主要实现复制粘贴内容，另外←→移动光标也需要后台代码控制。通过PreviewKeyDown事件捕获键盘左移右移，复制，删除等事件，做出相应处理：

private void Part2_KeyDown(object sender, System.Windows.Input.KeyEventArgs e){ if (e.Key == Key.Back && part2.Text == "") {  part1.Focus(); } if (e.Key == Key.Right && part2.CaretIndex == part2.Text.Length) {  part3.Focus();  e.Handled = true; } if (e.Key == Key.Left && part2.CaretIndex == 0) {  part1.Focus();  e.Handled = true; } if (e.KeyboardDevice.Modifiers.HasFlag(ModifierKeys.Control) && e.Key == Key.C) {  if (part2.SelectionLength == 0)  {   var vm = this.DataContext as IpAddressViewModel;   Clipboard.SetText(vm.AddressText);  } }}

通过DataObject.AddPastingHandler(part1, TextBox_Pasting)添加粘贴事件。使控件赋值。

2、通过ViewModel方式实现属性绑定通知，来控制焦点变化及内容赋值。

ViewModel类要实现绑定通知需要实现INotifyPropertyChanged接口中的方法。

我们新建一个IpAddressViewModel类继承INotifyPropertyChanged，代码如下：

public class IpAddressViewModel : INotifyPropertyChanged{ public event EventHandler AddressChanged; public string AddressText {  get { return $"{Part1??"0"}.{Part2??"0"}.{Part3??"0"}.{Part4??"0"}"; } } private bool isPart1Focused; public bool IsPart1Focused {  get { return isPart1Focused; }  set { isPart1Focused = value; OnPropertyChanged(); } } private string part1; public string Part1 {  get { return part1; }  set  {   part1 = value;   SetFocus(true, false, false, false);   var moveNext = CanMoveNext(ref part1);   OnPropertyChanged();   OnPropertyChanged(nameof(AddressText));   AddressChanged?.Invoke(this, EventArgs.Empty);   if (moveNext)   {    SetFocus(false, true, false, false);   }  } }  private bool isPart2Focused; public bool IsPart2Focused {  get { return isPart2Focused; }  set { isPart2Focused = value; OnPropertyChanged(); } } private string part2; public string Part2 {  get { return part2; }  set  {   part2 = value;   SetFocus(false, true, false, false);   var moveNext = CanMoveNext(ref part2);   OnPropertyChanged();   OnPropertyChanged(nameof(AddressText));   AddressChanged?.Invoke(this, EventArgs.Empty);   if (moveNext)   {    SetFocus(false, false, true, false);   }  } } private bool isPart3Focused; public bool IsPart3Focused {  get { return isPart3Focused; }  set { isPart3Focused = value; OnPropertyChanged(); } } private string part3; public string Part3 {  get { return part3; }  set  {   part3 = value;   SetFocus(false, false, true, false);   var moveNext = CanMoveNext(ref part3);   OnPropertyChanged();   OnPropertyChanged(nameof(AddressText));   AddressChanged?.Invoke(this, EventArgs.Empty);   if (moveNext)   {    SetFocus(false, false, false, true);   }  } } private bool isPart4Focused; public bool IsPart4Focused {  get { return isPart4Focused; }  set { isPart4Focused = value; OnPropertyChanged(); } } private string part4; public string Part4 {  get { return part4; }  set  {   part4 = value;   SetFocus(false, false, false, true);   var moveNext = CanMoveNext(ref part4);   OnPropertyChanged();   OnPropertyChanged(nameof(AddressText));   AddressChanged?.Invoke(this, EventArgs.Empty);  } }  public void SetAddress(string address) {  if (string.IsNullOrWhiteSpace(address))   return;  var parts = address.Split('.');     if (int.TryParse(parts[0], out var num0))  {   Part1 = num0.ToString();  }  if (int.TryParse(parts[1], out var num1))  {   Part2 = parts[1];  }  if (int.TryParse(parts[2], out var num2))  {   Part3 = parts[2];  }  if (int.TryParse(parts[3], out var num3))  {   Part4 = parts[3];  } } private bool CanMoveNext(ref string part) {  bool moveNext = false;  if (!string.IsNullOrWhiteSpace(part))  {   if (part.Length >= 3)   {    moveNext = true;   }   if (part.EndsWith("."))   {    moveNext = true;    part = part.Replace(".", "");   }  }  return moveNext; } private void SetFocus(bool part1, bool part2, bool part3, bool part4) {  IsPart1Focused = part1;  IsPart2Focused = part2;  IsPart3Focused = part3;  IsPart4Focused = part4; } public event PropertyChangedEventHandler PropertyChanged; protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null) {  PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName)); }}

到这里基本就完成了，生成控件然后到MainWindow中引用该控件