[英]Setting ComboBox DataSource to an enum and binding SelectedValue
我有點絕望,因為昨天它正在工作,但是今天它不再工作,請允許我解釋一下我要做什么:
我想將ComboBox
的DataSource
設置為特定枚舉中的所有枚舉值。 就像這樣:
cmbType.DataSource = m_addViewPresenter.Types;
其中Types是一個BindingList
並按如下方式初始化:
public BindingList<MyEnum> Types
{
get { return m_types; }
set
{
m_types = value;
OnPropertyChanged();
}
}
[ImportingConstructor]
public AddViewPresenter()
{
Types = new BindingList<MyEnum>(
Enum.GetValues(typeof(MyEnum))
.Cast<MyEnum>().ToList());
}
此外,我想將當前選擇的項目綁定到屬性。 由於ComboBox.SelectedItem
不會觸發INotifyProperty
事件,因此我正在使用ComboBox.SelectedValue
。
cmbType.Bind(m_addViewPresenter, c => c.SelectedValue, m => m.SelectedValue);
public static void Bind<TComponent, T>(
this TComponent component, T value,
Expression<Func<TComponent, object>> controlProperty,
Expression<Func<T, object>> modelProperty)
where TComponent : IBindableComponent
where T : INotifyPropertyChanged
{
var controlPropertyName = PropertyNameResolver.GetPropertyName(controlProperty);
var modelPropertyName = PropertyNameResolver.GetPropertyName(modelProperty);
component.DataBindings.Add(new Binding(controlPropertyName, value, modelPropertyName, false, DataSourceUpdateMode.OnPropertyChanged));
}
昨天工作正常,但是有些事情搞砸了,今天我只收到一個InvalidOperationException
:
無法在具有空ValueMember的ListControl中設置SelectedValue。
我知道它在黑暗中發掘,但是任何人都可以與我集思廣益並找出問題所在嗎? 提前致謝!
選項1
要將SelectedValue
用於數據綁定,請創建一個Calss DataItem:
public class DataItem
{
public MyEnum Value { get; set; }
public string Text { get; set; }
}
然后使用以下代碼進行數據綁定:
this.comboBox1.DataSource = Enum.GetValues(typeof(MyEnum)).Cast<MyEnum>()
.Select(x => new DataItem() { Value = x, Text = x.ToString() })
.ToList();
this.comboBox1.ValueMember = "Value";
this.comboBox1.DisplayMember = "Text";
this.comboBox1.DataBindings.Add(
new Binding("SelectedValue", yourObjectToBind, "PropertyOfYourObject"));
您可以使包含public T Value { get; set; }
通用DataItem<T>
public T Value { get; set; }
public T Value { get; set; }
public T Value { get; set; }
,使其在您的項目中更可重用。
選項2
要將SelectedItem
用於數據綁定:
this.comboBox1.DataSource = Enum.GetValues(typeof(MyEnum));
this.comboBox1.DataBindings.Add(
new Binding("SelectedItem", yourObjectToBind, "PropertyOfYourObject"));
選項3
要使用SelectedValue
進行數據綁定作為Ivan Stoev建議的另一個選項,您可以通過以下方式執行數據綁定:
this.comboBox1.DataSource = Enum.GetValues(typeof(MyEnum));
this.comboBox1.DataBindings.Add(
new Binding("SelectedValue", yourObjectToBind, "PropertyOfYourObject",
true, DataSourceUpdateMode.OnPropertyChanged));
Jannik編輯:
選項1的基本通用方法如下所示:
public class ComboBoxItemWrapper<T>
{
public T Value { get; set; }
public string Text { get; set; }
}
好的,就是這種情況。 您正在正確綁定到ComboBox.SelectedValue
。 問題來自以下行:
component.DataBindings.Add(new Binding(controlPropertyName, value, modelPropertyName, false, DataSourceUpdateMode.OnPropertyChanged));
它應該是
component.DataBindings.Add(new Binding(controlPropertyName, value, modelPropertyName, true, DataSourceUpdateMode.OnPropertyChanged));
不久,在使用WF數據綁定時,請始終將Binding.FormattingEnabled
設置為true
(如在我的示例中回答您的另一個問題),並且不會有任何問題。
從我對窗體上的Exchange UserControls的答案的修改示例, 其中帶有數據綁定,顯示了案例和解決方案:
using System;
using System.Drawing;
using System.Windows.Forms;
namespace Tests
{
enum MyEnum { Red, Green, }
class Controller
{
public MyEnum SelectedValue { get; set; }
}
static class Program
{
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
var form = new Form();
var topPanel = new Panel { Dock = DockStyle.Top, Parent = form };
var combo = new ComboBox { Left = 8, Top = 8, Parent = topPanel };
topPanel.Height = combo.Height + 16;
combo.DataSource = (MyEnum[])Enum.GetValues(typeof(MyEnum));
var c = new Controller();
combo.DataBindings.Add(new Binding("SelectedValue", c, "SelectedValue", true, DataSourceUpdateMode.OnPropertyChanged));
form.BindingContextChanged += (sender, e) =>
{
// If you change combo binding formatting enabled parameter to false,
// the next will throw the exception you are getting
c.SelectedValue = MyEnum.Red;
};
var panel1 = new Panel { Dock = DockStyle.Fill, Parent = form, BackColor = Color.Red };
var panel2 = new Panel { Dock = DockStyle.Fill, Parent = form, BackColor = Color.Green };
Bind(panel1, "Visible", combo, "SelectedValue", value => (MyEnum)value == MyEnum.Red);
Bind(panel2, "Visible", combo, "SelectedValue", value => (MyEnum)value == MyEnum.Green);
Application.Run(form);
}
static void Bind(Control target, string targetProperty, object source, string sourceProperty, Func<object, object> expression)
{
var binding = new Binding(targetProperty, source, sourceProperty, false, DataSourceUpdateMode.Never);
binding.Format += (sender, e) => e.Value = expression(e.Value);
target.DataBindings.Add(binding);
}
}
}
您可能還會發現以下有用的線程自定義WinForms數據綁定與轉換器不能在可為null的類型上使用(雙精度)?
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