Question

我是wpf的新手并且已经和这个问题斗争了好几天了。我有一个组合框，其dataview作为itemssource。它正确显示值，但重新运行应用程序时，selecteditem始终为null。

组合框绑定的ChargeCodeValidValues对象：

public class ChargeCodeValidValues
{
    #region Properties

    public DataTable ChargeCodesValidValuesTable { get; set; }
    public DataView dvChargeCodeValidValues { get; set; }       

    #endregion
    #region Constructor

    public ChargeCodeValidValues()
    {
        LoadChargeCodesValidValues();
    }

    public void LoadChargeCodesValidValues()
    {
        Database db = new Database();
        DataTable dataTable = db.ExecuteQuery("upGet_ChargeCodesValidValues", "ChargeCodesValidValues", "ID");

        this.ChargeCodesValidValuesTable = dataTable;
        this.dvChargeCodeValidValues = ChargeCodesValidValuesTable.DefaultView;
    }

XAML：

 <DataTemplate x:Key="combodescriptionTemplate">
      <ComboBox Name="cboCombo"
                Loaded="cboCombo_Loaded">
           <ComboBox.DataContext>
                <Objects:ChargeCodeValidValues/>
           </ComboBox.DataContext>
      </ComboBox>
 </DataTemplate>  

 <local:TotalCellTemplateSelector x:Key="totalcellTemplateSelector" 
           combodescriptionTemplate="{StaticResource combodescriptionTemplate}"/>

gridview专栏：

<dxg:GridColumn Header="Description" FieldName="Description" Width="Auto" MinWidth="132" AllowMoving="False" CellTemplateSelector="{StaticResource totalcellTemplateSelector}" /> -->

此列默认为文本框。它会根据其他列的值

更改为组合框

代码：

 private void cboCombo_Loaded(object sender, RoutedEventArgs e)
 {
      ComboBox cmb = sender as ComboBox;
      DataTable dtChargeCodeValidValues = oChargeCodesValidvalues.ChargeCodesValidValuesTable.Copy();
      DataView dvCurrentCodeValues = dtChargeCodeValidValues.Copy().DefaultView;
      cmb.ItemsSource = dvCurrentCodeValues;
      cmb.DisplayMemberPath = "Description";
      cmb.SelectedValuePath = "Description";
      cmb.SelectedValue = "Description";
 }

Answer 1

在应用程序的不同调用中，ComboBox中的选择不会持久存在。你必须自己编写代码。例如：

<ComboBox
    x:Name="comboBox"
    SelectionChanged="OnSelectionChanged"
    Loaded="OnComboBoxLoaded"
    >
    <ComboBox.Items>
        <system:String>One</system:String>
        <system:String>Two</system:String>
        <system:String>Three</system:String>
    </ComboBox.Items>
</ComboBox>

...使用以下代码隐藏：

private void OnSelectionChanged(object sender, SelectionChangedEventArgs e)
{
    int index = comboBox.SelectedIndex;
    using (IsolatedStorageFile store = IsolatedStorageFile.GetUserStoreForApplication())
    {
        using (IsolatedStorageFileStream stream = store.CreateFile("selectedIndex"))
        {
            using (BinaryWriter writer = new BinaryWriter(stream))
            {
                writer.Write(index.ToString());
            }
        }
    }
}

private void OnComboBoxLoaded(object sender, RoutedEventArgs e)
{
    int index = GetPreviousIndex();
    comboBox.SelectedIndex = index;
    comboBox.Text = comboBox.Items[index] as string;
}

private int GetPreviousIndex()
{
    using (IsolatedStorageFile store = IsolatedStorageFile.GetUserStoreForApplication())
    {
        using (IsolatedStorageFileStream stream = store.OpenFile("selectedIndex", FileMode.Open))
        {
            using (BinaryReader reader = new BinaryReader(stream))
            {
                try
                {
                    return int.Parse(reader.ReadString());
                }
                catch (Exception x)
                {
                    return -1;
                }
            }
        }
    }
}

请注意，设置SelectedIndex是不够的;您还必须设置Text属性，否则您无法在不打开ComboBox的情况下看到所选内容。

当然，有很多方法可以坚持选择;在这里，我只是快速拼凑了一些东西（有些肮脏）。

wpf combobox没有正确更新

1 个答案: