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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(nameof(path));
if (string.IsNullOrWhiteSpace(path))
throw new ArgumentException("path can not be an empty string", nameof(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]
[EditorBrowsable(EditorBrowsableState.Never)]
public static Binding Create<TSource>(Expression<Func<TSource, object>> propertyGetter, BindingMode mode = BindingMode.Default, IValueConverter converter = null, object converterParameter = null,
string stringFormat = null)
{
if (propertyGetter == null)
throw new ArgumentNullException(nameof(propertyGetter));
return new Binding(GetBindingPath(propertyGetter), 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 context, BindableObject bindObj, BindableProperty targetProperty, bool fromBindingContextChanged = false)
{
object src = _source;
var isApplied = IsApplied;
base.Apply(src ?? context, bindObj, targetProperty, fromBindingContextChanged: fromBindingContextChanged);
if (src != null && isApplied && fromBindingContextChanged)
return;
object bindingContext = src ?? Context ?? context;
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,
TargetNullValue = TargetNullValue,
FallbackValue = FallbackValue,
};
}
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]
[EditorBrowsable(EditorBrowsableState.Never)]
static string GetBindingPath<TSource>(Expression<Func<TSource, object>> 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<string>(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<DefaultMemberAttribute>().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();
}
}
}
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