以字符串形式筛选组合框中选定的项目

Question

我正试图使用ComboBox.SelectedItem在DataGrid上进行筛选，但我在作为string访问SelectedItem时遇到问题。这就是我迄今为止所尝试的；

foreach (ComboBoxItem cItem in departmentComboBox.ItemsSource)
{
    if (departmentComboBox.SelectedItem != null)
    {
        criteria.Add(new Predicate<EmployeeModel>(x => x.Department == departmentComboBox.SelectedItem as string));
        break;
    }
}

这导致了一个异常；

Additional information: Unable to cast object of type 'System.String' to type 'System.Windows.Controls.ComboBoxItem'.

CCD_ 5属于CCD_。如何正确访问SelectedItem，以便在筛选方法中正确使用它？

编辑：显示如何添加组合框项目；

List<string> distinctList = Employees.Select(i => i.Department).Distinct().ToList();
distinctList.Insert(0, "Everyone");
distinctList.Sort();
departmentComboBox.ItemsSource = distinctList;

Answer 1

您可以这样尝试：

foreach (ComboBoxItem cItem in departmentComboBox.ItemsSource){
if (departmentComboBox.SelectedItem != null)
{
    string selectedItemName = this.departmentComboBox.GetItemText(this.departmentComboBox.SelectedItem);
    criteria.Add(new Predicate<EmployeeModel>(x => x.Department.Equals(selectedItemName)));
    break;}
}

Answer 2

您可以使用SelectedItem的ToString()方法。

foreach (ComboBoxItem cItem in departmentComboBox.ItemsSource)
{
    if (departmentComboBox.SelectedItem != null)
    {
        criteria.Add(new Predicate<EmployeeModel>(x => x.Department == departmentComboBox.SelectedItem.ToString()));
        break;
    }
}

确保组合框的项目中没有null值，否则可以使用以下代码：

foreach (ComboBoxItem cItem in departmentComboBox.ItemsSource)
{
    if (departmentComboBox.SelectedItem != null)
    {
        criteria.Add(new Predicate<EmployeeModel>(x => x.Department == "" + departmentComboBox.SelectedItem));
        break;
    }
}

Answer 3

您正在通过项源创建一个字符串列表来填充组合框，这很好，但困惑在于如何访问它们。再次使用ItemSource将返回相同的字符串列表，然后您将尝试检查每个字符串是否与所选字符串相同。获取所选项目的更好方法是通过.SelectedItem属性。首先检查Null，你也可以放弃for循环：）

        if (departmentComboBox.SelectedItem != null)
        {
            criteria.Add(new Predicate<EmployeeModel>(x => x.Department == departmentComboBox.SelectedItem as string));
        }