using System; using System.Collections.Generic; using System.ComponentModel; using System.Globalization; using System.Linq; using System.Linq.Expressions; using System.Reflection; using System.Text; using Xamarin.Forms.Internals; namespace Xamarin.Forms { public sealed class Binding : BindingBase { internal const string SelfPath = "."; IValueConverter _converter; object _converterParameter; BindingExpression _expression; string _path; object _source; string _updateSourceEventName; public Binding() { } public Binding(string path, BindingMode mode = BindingMode.Default, IValueConverter converter = null, object converterParameter = null, string stringFormat = null, object source = null) { if (path == null) throw new ArgumentNullException("path"); if (string.IsNullOrWhiteSpace(path)) throw new ArgumentException("path can not be an empty string", "path"); Path = path; Converter = converter; ConverterParameter = converterParameter; Mode = mode; StringFormat = stringFormat; Source = source; } public IValueConverter Converter { get { return _converter; } set { ThrowIfApplied(); _converter = value; } } public object ConverterParameter { get { return _converterParameter; } set { ThrowIfApplied(); _converterParameter = value; } } public string Path { get { return _path; } set { ThrowIfApplied(); _path = value; _expression = new BindingExpression(this, !string.IsNullOrWhiteSpace(value) ? value : SelfPath); } } public object Source { get { return _source; } set { ThrowIfApplied(); _source = value; } } [EditorBrowsable(EditorBrowsableState.Never)] public string UpdateSourceEventName { get { return _updateSourceEventName; } set { ThrowIfApplied(); _updateSourceEventName = value; } } [Obsolete] public static Binding Create(Expression> propertyGetter, BindingMode mode = BindingMode.Default, IValueConverter converter = null, object converterParameter = null, string stringFormat = null) { if (propertyGetter == null) throw new ArgumentNullException("propertyGetter"); string path = GetBindingPath(propertyGetter); return new Binding(path, mode, converter, converterParameter, stringFormat); } internal override void Apply(bool fromTarget) { base.Apply(fromTarget); if (_expression == null) _expression = new BindingExpression(this, SelfPath); _expression.Apply(fromTarget); } internal override void Apply(object newContext, BindableObject bindObj, BindableProperty targetProperty, bool fromBindingContextChanged = false) { object src = _source; var isApplied = IsApplied; base.Apply(src ?? newContext, bindObj, targetProperty, fromBindingContextChanged: fromBindingContextChanged); if (src != null && isApplied && fromBindingContextChanged) return; object bindingContext = src ?? Context ?? newContext; if (_expression == null && bindingContext != null) _expression = new BindingExpression(this, SelfPath); _expression.Apply(bindingContext, bindObj, targetProperty); } internal override BindingBase Clone() { return new Binding(Path, Mode) { Converter = Converter, ConverterParameter = ConverterParameter, StringFormat = StringFormat, Source = Source, UpdateSourceEventName = UpdateSourceEventName }; } internal override object GetSourceValue(object value, Type targetPropertyType) { if (Converter != null) value = Converter.Convert(value, targetPropertyType, ConverterParameter, CultureInfo.CurrentUICulture); return base.GetSourceValue(value, targetPropertyType); } internal override object GetTargetValue(object value, Type sourcePropertyType) { if (Converter != null) value = Converter.ConvertBack(value, sourcePropertyType, ConverterParameter, CultureInfo.CurrentUICulture); return base.GetTargetValue(value, sourcePropertyType); } internal override void Unapply(bool fromBindingContextChanged = false) { if (Source != null && fromBindingContextChanged && IsApplied) return; base.Unapply(fromBindingContextChanged: fromBindingContextChanged); if (_expression != null) _expression.Unapply(); } [Obsolete] static string GetBindingPath(Expression> propertyGetter) { Expression expr = propertyGetter.Body; var unary = expr as UnaryExpression; if (unary != null) expr = unary.Operand; var builder = new StringBuilder(); var indexed = false; var member = expr as MemberExpression; if (member == null) { var methodCall = expr as MethodCallExpression; if (methodCall != null) { if (methodCall.Arguments.Count == 0) throw new ArgumentException("Method calls are not allowed in binding expression"); var arguments = new List(methodCall.Arguments.Count); foreach (Expression arg in methodCall.Arguments) { if (arg.NodeType != ExpressionType.Constant) throw new ArgumentException("Only constants can be used as indexer arguments"); object value = ((ConstantExpression)arg).Value; arguments.Add(value != null ? value.ToString() : "null"); } Type declarerType = methodCall.Method.DeclaringType; DefaultMemberAttribute defaultMember = declarerType.GetTypeInfo().GetCustomAttributes(typeof(DefaultMemberAttribute), true).OfType().FirstOrDefault(); string indexerName = defaultMember != null ? defaultMember.MemberName : "Item"; MethodInfo getterInfo = declarerType.GetProperties().Where(pi => pi.Name == indexerName && pi.CanRead && pi.GetMethod.IsPublic && !pi.GetMethod.IsStatic).Select(pi => pi.GetMethod).FirstOrDefault(); if (getterInfo != null) { if (getterInfo == methodCall.Method) { indexed = true; builder.Append("["); var first = true; foreach (string argument in arguments) { if (!first) builder.Append(","); builder.Append(argument); first = false; } builder.Append("]"); member = methodCall.Object as MemberExpression; } else throw new ArgumentException("Method calls are not allowed in binding expressions"); } else throw new ArgumentException("Public indexer not found"); } else throw new ArgumentException("Invalid expression type"); } while (member != null) { var property = (PropertyInfo)member.Member; if (builder.Length != 0) { if (!indexed) builder.Insert(0, "."); else indexed = false; } builder.Insert(0, property.Name); // member = member.Expression as MemberExpression ?? (member.Expression as UnaryExpression)?.Operand as MemberExpression; member = member.Expression as MemberExpression ?? (member.Expression is UnaryExpression ? (member.Expression as UnaryExpression).Operand as MemberExpression : null); } return builder.ToString(); } } }