当我输入第一个字母时，如何在组合框中搜索 [英] how to search in combo box when I type first letter
本文介绍了当我输入第一个字母时，如何在组合框中搜索的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我想知道当我在组合框中输入第一个字符时，它应该显示所有开始该字符的项目，并且字符保留在组合框文本编辑中。
xmlns：myControl =clr-namespace：Enrollment.Controls
< myControl：AutoCompleteComboBox Grid.Row = 7 网格。列 = 1 SelectedValue = {Binding Path = SelectedCurrentCity} ItemsSource = < span class =code-keyword> {Binding Path = CurrentCityList} >
我添加了一个控件
< UserControl x：Class = Enrollment.Controls.AutoCompleteComboBox
xmlns = http://schemas.microsoft.com/winfx/2006/xaml/presentation
xmlns：x = http://schemas.microsoft.com/winfx/2006/xaml
>
< 画布 >
< < span class =code-leadattribute> TextBox x：名称 = autoTextBox 高度 = 25 MinWidth = 240 TextWrapping = NoWrap > < span class =code-keyword>< / TextBox >
< ComboBox MinWidth = 240 x：名称 = suggestionListBox 保证金 = 0,25,0，-25 已移除 = LightYellow
< span class =code-attribute> 可见性 = 折叠 SelectionChanged = suggestionListBox_SelectionChanged / >
< / Canvas >
< / UserControl > ;
public Windows2（）
{
fillCurrentCityList（）;
}
public fillCurrentCityList（）
{
CurrentCityList = new List< string>（）;
string tt1 = CurrStateIDcmb.SelectedValue.ToString（）;
string str1 = 从mstCity中选择CityName其中StateId =（从mstState中选择StateId，其中StateName = @ tt1）;
SqlConnection cn2 = new SqlConnection（ @ 数据源= SUMIT \SQLEXPRESS; AttachDbFilename ='C：\Program Files \ Microsoft SQL Server \ MSSQL.1 \ MSSQL \Data\Enrollment.mdf'; Integrated Security = True） ;
SqlCommand cmd2 = new SqlCommand（str1，cn2）;
cn2.Open（）;
cmd2.Parameters.AddWithValue（ @ tt1 ，CurrStateIDcmb.SelectedValue.ToString（））;
SqlDataReader dm;
尝试
{
dm = cmd2.ExecuteReader（）;
while （dm.Read（））
{
CurrentCityList.Add（dm [< span class =code-string> CityName]。ToString（））;
}
}
catch （例外情况）
{
}
最后
{
cn2.Close（） ;
}
}
public partial class AutoCompleteComboBox：UserControl
{
#region构造函数
public AutoCompleteComboBox（）
{
InitializeComponent（）;
// 将事件附加到控件
autoTextBox.TextChanged + =
new TextChangedEventHandler（autoTextBox_TextChanged）;
autoTextBox.PreviewKeyDown + =
new KeyEventHandler（autoTextBox_PreviewKeyDown）;
suggestionListBox.SelectionChanged + =
new SelectionChangedEventHandler（suggestionListBox_SelectionChanged）;
}
#endregion
#region属性
/// < ; 摘要 >
/// 获取或设置项目来源。
/// < / summary >
/// < value < span class =code-summarycomment>> 项目来源。< / value >
public IEnumerable< string> ItemsSource
{
get
{
return （ IEnumerable的<串GT）的GetValue（ItemsSourceProperty）;
}
set {SetValue（ItemsSourceProperty， value ）; }
}
// 使用DependencyProperty作为ItemsSource的后备存储。
// 这可以实现动画，样式，装订等......
public static readonly DependencyProperty ItemsSourceProperty = DependencyProperty.Register（ ItemsSource
， typeof （IEnumerable< string>）
， typeof （AutoCompleteComboBox）
， new UIPropertyMetadata（ null ））;
/// < 摘要 >
/// 获取或设置选定的值。
/// < / summary >
/// < value < span class =code-summarycomment>> 所选值。< / value >
public string SelectedValue
{
get { return （串）的GetValue（SelectedValueProperty）; }
set {SetValue（SelectedValueProperty， value ）; }
}
// 使用DependencyProperty作为SelectedValue的后备存储。
// 这可以实现动画，样式，装订等......
public static readonly DependencyProperty SelectedValueProperty =
DependencyProperty.Register（ SelectedValue
， typeof （ string ）
， typeof （AutoCompleteComboBox ）
， new UIPropertyMetadata（ string .Empty））;
#endregion
#region方法
/// < 摘要 >
/// 处理autoTextBox控件的TextChanged事件。
/// < / summary >
/// < param < span class =code-summarycomment> name =sender > 来源事件。< / param >
/// < param name =e > 包含事件数据的实例。< / param >
void autoTextBox_TextChanged（ object sender，TextChangedEventArgs e）
{
// 仅限有文本时自动填写
如果（autoTextBox.Text.Length > 0 ）
{
// 使用Linq查询itemsSource以获取resultdata
字符串 condition = string .Format （ {0}％，autoTextBox.Text）;
IEnumerable< string> results = ItemsSource.Where（ delegate （ string s）{ return s.ToLower（）。StartsWith（autoTextBox.Text.ToLower（））;
}
）;
if （results.Count（）> 0 ）
{
suggestionListBox.ItemsSource = results;
suggestionListBox.Visibility = Visibility.Visible;
}
else
{
suggestionListBox.Visibility = Visibility.Collapsed;
suggestionListBox.ItemsSource = null ;
}
}
else
{
suggestionListBox.Visibility = Visibility.Collapsed;
suggestionListBox.ItemsSource = null ;
}
}
/// < 摘要 >
/// 处理autoTextBox控件的PreviewKeyDown事件。
/// < / summary >
/// < param < span class =code-summarycomment> name =sender > 来源事件。< / param >
/// < param name =e > 包含事件数据的实例。< / param >
void autoTextBox_PreviewKeyDown（ object sender，KeyEventArgs e）
{
if （e.Key == Key.Down）
{
if （suggestionListBox.SelectedIndex < suggestionListBox.Items.Count）
{
suggestionListBox.SelectedIndex = suggestionListBox.SelectedIndex + 1 ;
}
}
如果（e.Key == Key.Up）
{
if （suggestionListBox.SelectedIndex > -1）
{
suggestionListBox.SelectedIndex = suggestionListBox .SelectedIndex - 1 ;
}
}
if （e.Key == Key.Enter || e.Key == Key.Tab）
{
// 提交选择
suggestionListBox.Visibility = Visibility .Collapsed;
e.Handled =（e.Key == Key.Enter）;
}
if （e.Key == Key.Escape）
{
// 取消选择
suggestionListBox.ItemsSource = null < /跨度>;
suggestionListBox.Visibility = Visibility.Collapsed;
}
}
/// < 摘要 >
/// 处理suggestionListBox控件的SelectionChanged事件。
/// < / summary >
/// < param < span class =code-summarycomment> name =sender > 来源事件。< / param >
/// < param name =e > < 参见 cref =System.Windows.Controls.SelectionChangedEventArgs/ > 包含事件数据的实例。< / param >
private void suggestionListBox_SelectionChanged（ object sender，SelectionChangedEventArgs e）
{
if （suggestionListBox.ItemsSource！= null ）
{
autoTextBox.TextChanged - = new TextChangedEventHandler（autoTextBox_TextChanged）;
if （suggestionListBox.SelectedIndex！= -1）
{
autoTextBox.Text = suggestionListBox.SelectedItem.ToString（）;
}
autoTextBox.TextChanged + = new TextChangedEventHandler（autoTextBox_TextChanged）;
}
}
#endregion
}
autoTextBox_TextChanged中的异常
ItemsSource显示为null
http://screencast.com/t/ObdoUxAmW [ ^ ]
解决方案
请看这些例子：
1. 自动过滤WPF中的ComboBox [ ^ ]
2. 可重复使用的WPF自动完成文本框 [ ^ ]
public fillCurrentCityList（）
{
CurrentCityList = new List< string>（）;
string tt1 = CurrStateIDcmb.SelectedValue.ToString（）;
string str1 = 从mstCity中选择CityName其中StateId =（从mstState中选择StateId，其中StateName = @ tt1）;
SqlConnection cn2 = new SqlConnection（ @ 数据源= SUMIT \SQLEXPRESS; AttachDbFilename ='C：\Program Files \ Microsoft SQL Server \ MSSQL.1 \ MSSQL \Data\Enrollment.mdf'; Integrated Security = True） ;
SqlCommand cmd2 = new SqlCommand（str1，cn2）;
cn2.Open（）;
cmd2.Parameters.AddWithValue（ @ tt1 ，CurrStateIDcmb.SelectedValue.ToString（））;
this .DataContext = this ; // 这是解决方案
SqlDataReader dm;
尝试
{
dm = cmd2.ExecuteReader（）;
while （dm.Read（））
{
CurrentCityList.Add（dm [< span class =code-string> CityName]。ToString（））;
}
}
catch （例外情况）
{
}
最后
{
cn2.Close（） ;
}
} < / string >
I want to know that when I type a first character in combo box it should display all item which are start that character and the character remains in combo box text edit.
xmlns:myControl="clr-namespace:Enrollment.Controls"
<myControl:AutoCompleteComboBox Grid.Row="7" Grid.Column="1" SelectedValue="{Binding Path=SelectedCurrentCity}" ItemsSource="{Binding Path=CurrentCityList}">
I have added a control
<UserControl x:Class="Enrollment.Controls.AutoCompleteComboBox"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
>
<Canvas>
<TextBox x:Name="autoTextBox" Height="25" MinWidth="240" TextWrapping="NoWrap"></TextBox>
<ComboBox MinWidth="240" x:Name="suggestionListBox" Margin="0,25,0,-25" removed="LightYellow"
Visibility="Collapsed" SelectionChanged="suggestionListBox_SelectionChanged" />
</Canvas>
</UserControl>
public Windows2()
{
fillCurrentCityList();
}
public fillCurrentCityList ()
{
CurrentCityList = new List<string>();
string tt1 = CurrStateIDcmb.SelectedValue.ToString();
string str1 = "Select CityName from mstCity where StateId = (Select StateId from mstState where StateName =@tt1)";
SqlConnection cn2 = new SqlConnection(@"Data Source=SUMIT\SQLEXPRESS;AttachDbFilename='C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Data\Enrollment.mdf';Integrated Security=True");
SqlCommand cmd2 = new SqlCommand(str1, cn2);
cn2.Open();
cmd2.Parameters.AddWithValue("@tt1", CurrStateIDcmb.SelectedValue.ToString());
SqlDataReader dm;
try
{
dm = cmd2.ExecuteReader();
while (dm.Read())
{
CurrentCityList.Add(dm["CityName"].ToString());
}
}
catch (Exception ex)
{
}
finally
{
cn2.Close();
}
}
public partial class AutoCompleteComboBox : UserControl
{
#region Constructor
public AutoCompleteComboBox()
{
InitializeComponent();
// Attach events to the controls
autoTextBox.TextChanged +=
new TextChangedEventHandler(autoTextBox_TextChanged);
autoTextBox.PreviewKeyDown +=
new KeyEventHandler(autoTextBox_PreviewKeyDown);
suggestionListBox.SelectionChanged +=
new SelectionChangedEventHandler(suggestionListBox_SelectionChanged);
}
#endregion
#region Properties
/// <summary>
/// Gets or sets the items source.
/// </summary>
/// <value>The items source.</value>
public IEnumerable<string> ItemsSource
{
get
{
return (IEnumerable<string>)GetValue(ItemsSourceProperty);
}
set { SetValue(ItemsSourceProperty, value); }
}
// Using a DependencyProperty as the backing store for ItemsSource.
// This enables animation, styling, binding, etc...
public static readonly DependencyProperty ItemsSourceProperty =DependencyProperty.Register("ItemsSource"
, typeof(IEnumerable<string>)
, typeof(AutoCompleteComboBox)
, new UIPropertyMetadata(null));
/// <summary>
/// Gets or sets the selected value.
/// </summary>
/// <value>The selected value.</value>
public string SelectedValue
{
get { return (string)GetValue(SelectedValueProperty); }
set { SetValue(SelectedValueProperty, value); }
}
// Using a DependencyProperty as the backing store for SelectedValue.
// This enables animation, styling, binding, etc...
public static readonly DependencyProperty SelectedValueProperty =
DependencyProperty.Register("SelectedValue"
, typeof(string)
, typeof(AutoCompleteComboBox)
, new UIPropertyMetadata(string.Empty));
#endregion
#region Methods
/// <summary>
/// Handles the TextChanged event of the autoTextBox control.
/// </summary>
/// <param name="sender">The source of the event.</param>
/// <param name="e">The instance containing the event data.</param>
void autoTextBox_TextChanged(object sender, TextChangedEventArgs e)
{
// Only autocomplete when there is text
if (autoTextBox.Text.Length > 0)
{
// Use Linq to Query ItemsSource for resultdata
string condition = string.Format("{0}%", autoTextBox.Text);
IEnumerable<string> results = ItemsSource.Where(delegate(string s){return s.ToLower().StartsWith(autoTextBox.Text.ToLower());
}
);
if (results.Count() > 0)
{
suggestionListBox.ItemsSource = results;
suggestionListBox.Visibility = Visibility.Visible;
}
else
{
suggestionListBox.Visibility = Visibility.Collapsed;
suggestionListBox.ItemsSource = null;
}
}
else
{
suggestionListBox.Visibility = Visibility.Collapsed;
suggestionListBox.ItemsSource = null;
}
}
/// <summary>
/// Handles the PreviewKeyDown event of the autoTextBox control.
/// </summary>
/// <param name="sender">The source of the event.</param>
/// <param name="e">The instance containing the event data.</param>
void autoTextBox_PreviewKeyDown(object sender, KeyEventArgs e)
{
if (e.Key == Key.Down)
{
if (suggestionListBox.SelectedIndex < suggestionListBox.Items.Count)
{
suggestionListBox.SelectedIndex = suggestionListBox.SelectedIndex + 1;
}
}
if (e.Key == Key.Up)
{
if (suggestionListBox.SelectedIndex > -1)
{
suggestionListBox.SelectedIndex = suggestionListBox.SelectedIndex - 1;
}
}
if (e.Key == Key.Enter || e.Key == Key.Tab)
{
// Commit the selection
suggestionListBox.Visibility = Visibility.Collapsed;
e.Handled = (e.Key == Key.Enter);
}
if (e.Key == Key.Escape)
{
// Cancel the selection
suggestionListBox.ItemsSource = null;
suggestionListBox.Visibility = Visibility.Collapsed;
}
}
/// <summary>
/// Handles the SelectionChanged event of the suggestionListBox control.
/// </summary>
/// <param name="sender">The source of the event.</param>
/// <param name="e">The <see cref="System.Windows.Controls.SelectionChangedEventArgs"/> instance containing the event data.</param>
private void suggestionListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
if (suggestionListBox.ItemsSource != null)
{
autoTextBox.TextChanged -= new TextChangedEventHandler(autoTextBox_TextChanged);
if (suggestionListBox.SelectedIndex != -1)
{
autoTextBox.Text = suggestionListBox.SelectedItem.ToString();
}
autoTextBox.TextChanged += new TextChangedEventHandler(autoTextBox_TextChanged);
}
}
#endregion
}
Exception in autoTextBox_TextChanged
ItemsSource shows null
http://screencast.com/t/ObdoUxAmW[^]
解决方案
Please see these examples:
1. Automatically Filtering a ComboBox in WPF [^]
2. A Reusable WPF Autocomplete TextBox [^]
public fillCurrentCityList () { CurrentCityList = new List<string>(); string tt1 = CurrStateIDcmb.SelectedValue.ToString(); string str1 = "Select CityName from mstCity where StateId = (Select StateId from mstState where StateName =@tt1)"; SqlConnection cn2 = new SqlConnection(@"Data Source=SUMIT\SQLEXPRESS;AttachDbFilename='C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Data\Enrollment.mdf';Integrated Security=True"); SqlCommand cmd2 = new SqlCommand(str1, cn2); cn2.Open(); cmd2.Parameters.AddWithValue("@tt1", CurrStateIDcmb.SelectedValue.ToString()); this.DataContext = this; //this is the solution SqlDataReader dm; try { dm = cmd2.ExecuteReader(); while (dm.Read()) { CurrentCityList.Add(dm["CityName"].ToString()); } } catch (Exception ex) { } finally { cn2.Close(); } }</string>
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