当我希望将控件绑定到对象的属性时,必须提供属性的名称作为字符串。这不是很好,因为:
是否有一种设计模式可以解决此问题,但仍易于使用数据绑定?
(这是WinForms,ASP.NET和WPF以及其他系统中的问题。)
现在,我发现“ C#中的nameof()运算符的变通办法:typesafe数据绑定 ”也为解决方案提供了良好的起点。
如果您愿意在编译代码后使用后处理器,那么NotifyPropertyWeaver值得一看。
当绑定是用XML而不是C#完成时,有人知道WPF的一种好的解决方案吗?
感谢Oliver让我入门,现在我有了一个既支持重构又是类型安全的解决方案。它也让我实现INotifyPropertyChanged,以便处理重命名的属性。
它的用法如下:
checkBoxCanEdit.Bind(c => c.Checked, person, p => p.UserCanEdit); textBoxName.BindEnabled(person, p => p.UserCanEdit); checkBoxEmployed.BindEnabled(person, p => p.UserCanEdit); trackBarAge.BindEnabled(person, p => p.UserCanEdit); textBoxName.Bind(c => c.Text, person, d => d.Name); checkBoxEmployed.Bind(c => c.Checked, person, d => d.Employed); trackBarAge.Bind(c => c.Value, person, d => d.Age); labelName.BindLabelText(person, p => p.Name); labelEmployed.BindLabelText(person, p => p.Employed); labelAge.BindLabelText(person, p => p.Age);
person类显示了如何以一种类型安全的方式实现INotifyPropertyChanged(或查看此答案以获取实现INotifyPropertyChanged的另一种相当不错的方法,ActiveSharp- 自动INotifyPropertyChanged也看起来不错):
public class Person : INotifyPropertyChanged { private bool _employed; public bool Employed { get { return _employed; } set { _employed = value; OnPropertyChanged(() => c.Employed); } } // etc private void OnPropertyChanged(Expression<Func<object>> property) { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(BindingHelper.Name(property))); } } public event PropertyChangedEventHandler PropertyChanged; }
WinForms绑定帮助程序类包含了使它们全部工作的基础:
namespace TypeSafeBinding { public static class BindingHelper { private static string GetMemberName(Expression expression) { // The nameof operator was implemented in C# 6.0 with .NET 4.6 // and VS2015 in July 2015. // The following is still valid for C# < 6.0 switch (expression.NodeType) { case ExpressionType.MemberAccess: var memberExpression = (MemberExpression) expression; var supername = GetMemberName(memberExpression.Expression); if (String.IsNullOrEmpty(supername)) return memberExpression.Member.Name; return String.Concat(supername, '.', memberExpression.Member.Name); case ExpressionType.Call: var callExpression = (MethodCallExpression) expression; return callExpression.Method.Name; case ExpressionType.Convert: var unaryExpression = (UnaryExpression) expression; return GetMemberName(unaryExpression.Operand); case ExpressionType.Parameter: case ExpressionType.Constant: //Change return String.Empty; default: throw new ArgumentException("The expression is not a member access or method call expression"); } } public static string Name<T, T2>(Expression<Func<T, T2>> expression) { return GetMemberName(expression.Body); } //NEW public static string Name<T>(Expression<Func<T>> expression) { return GetMemberName(expression.Body); } public static void Bind<TC, TD, TP>(this TC control, Expression<Func<TC, TP>> controlProperty, TD dataSource, Expression<Func<TD, TP>> dataMember) where TC : Control { control.DataBindings.Add(Name(controlProperty), dataSource, Name(dataMember)); } public static void BindLabelText<T>(this Label control, T dataObject, Expression<Func<T, object>> dataMember) { // as this is way one any type of property is ok control.DataBindings.Add("Text", dataObject, Name(dataMember)); } public static void BindEnabled<T>(this Control control, T dataObject, Expression<Func<T, bool>> dataMember) { control.Bind(c => c.Enabled, dataObject, dataMember); } } }
这利用了C#3.5中的许多新内容,并显示了可能的结果。现在,如果只有卫生宏,那么 Lisp程序员可能会停止称我们为二等公民)