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@AnthonyDGreen AnthonyDGreen/XmlExtensions.vb Secret
Created Jun 16, 2019

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A sample of the bridge methods written to map pattern-based XML literals to XAML that supports Xamarin.Forms views based on the draft version of the pattern as of the week of 6/10/2019.
Imports System.Runtime.CompilerServices
Imports Xamarin.Forms
Module XmlExtensions
#Region " Properties with binding and/or type converters "
<Extension>
Sub SetFontSize(instance As Label,
value As Double,
valueText As String,
otherValue As Object)
If otherValue IsNot Nothing Then
Throw New NotImplementedException()
End If
' TODO: Consider passing a flag indicating whether the value is 0.0 because the developer
' wrote "0.0" in such cases to simplify tests for bridge method authors.
' Don't use Boolean? because like WPF CheckBox.IsChecked are naturally that type.
If value <> 0.0 OrElse valueText = "0" OrElse valueText = "0.0" Then
instance.FontSize = value
Return
End If
instance.FontSize = DirectCast(New FontSizeConverter().ConvertFromInvariantString(valueText), Double)
Return
'Dim namedSize As NamedSize
'Select Case valueText
' Case "micro"
' namedSize = NamedSize.Micro
' Case "small"
' namedSize = NamedSize.Small
' Case "medium"
' namedSize = NamedSize.Medium
' Case "large"
' namedSize = NamedSize.Large
' Case "default"
' namedSize = NamedSize.Default
' Case Else
' Throw New FormatException(valueText)
'End Select
'instance.FontSize = Device.GetNamedSize(namedSize, GetType(Label))
End Sub
<Extension>
Sub SetText(instance As Entry,
value As String,
valueText As String,
otherValue As Object)
If otherValue IsNot Nothing Then
Throw New NotSupportedException()
End If
If valueText?.StartsWith("{") Then
If valueText.StartsWith("{Binding ") AndAlso valueText.EndsWith("}") Then
Dim propertyName = valueText.Substring(9, valueText.Length - 9 - 1)
instance.SetBinding(Entry.TextProperty, New Binding(propertyName))
Else
Throw New FormatException(valueText)
End If
Else
instance.Text = value
End If
End Sub
<Extension>
Sub SetKeyboard(instance As Entry,
value As Keyboard,
valueText As String,
otherValue As Object)
If otherValue IsNot Nothing Then
Throw New NotSupportedException()
End If
If value IsNot Nothing Then
instance.Keyboard = value
Return
End If
If valueText?.StartsWith("{") Then
If valueText.StartsWith("{Binding ") AndAlso valueText.EndsWith("}") Then
Dim propertyName = valueText.Substring(9, valueText.Length - 9 - 1)
instance.SetBinding(Entry.KeyboardProperty, New Binding(propertyName))
Else
Throw New FormatException(valueText)
End If
Else
instance.Keyboard = New KeyboardTypeConverter().ConvertFromInvariantString(valueText)
End If
End Sub
<Extension>
Sub SetVerticalOptions(instance As View,
value As LayoutOptions,
valueText As String,
otherValue As Object)
SetPropertyIfNotDefaultWithSupportForTypeConvertersAndBinding(Of LayoutOptions, LayoutOptionsConverter)(
instance.VerticalOptions,
value,
valueText,
otherValue,
Function(left, right) left.Alignment = right.Alignment AndAlso left.Expands = right.Expands,
Nothing,
instance,
View.VerticalOptionsProperty)
End Sub
Private Sub SetPropertyIfNotDefaultWithSupportForTypeConvertersAndBinding(Of TValue As Structure, TConverter As {New, TypeConverter})(
ByRef backingStore As TValue,
value As TValue,
valueText As String,
otherValue As Object,
equals As Func(Of TValue, TValue, Boolean),
defaultValueText As String,
instance As BindableObject,
bindableProperty As BindableProperty
)
If Not equals(value, Nothing) OrElse valueText = defaultValueText Then
backingStore = value
Return
ElseIf otherValue IsNot Nothing Then
If TypeOf otherValue Is TValue Then
backingStore = otherValue
Return
End If
Dim asBinding = TryCast(otherValue, Binding)
If asBinding IsNot Nothing Then
instance.SetBinding(bindableProperty, asBinding)
Return
End If
Throw New InvalidOperationException()
ElseIf valueText.StartsWith("{") Then
If valueText.StartsWith("{Binding ") AndAlso valueText.EndsWith("}") Then
Dim propertyName = valueText.Substring(9, valueText.Length - 9 - 1)
instance.SetBinding(bindableProperty, New Binding(propertyName))
Else
Throw New FormatException(valueText)
End If
Else
backingStore = New TConverter().ConvertFromInvariantString(valueText)
End If
End Sub
Private Sub SetPropertyIfNotDefaultWithSupportForTypeConvertersAndBinding(Of TValue As Class, TConverter As {New, TypeConverter})(
ByRef backingStore As TValue,
value As TValue,
valueText As String,
otherValue As Object,
instance As BindableObject,
bindableProperty As BindableProperty
)
#If DEBUG Then
If GetType(TValue) Is GetType(String) Then Throw New InvalidOperationException("Wrong method for strings.")
#End If
If value IsNot Nothing Then
backingStore = value
Return
ElseIf otherValue Is Nothing AndAlso valueText Is Nothing Then
backingStore = Nothing
Return
ElseIf otherValue IsNot Nothing Then
Dim asTValue = TryCast(otherValue, TValue)
If asTValue IsNot Nothing Then
backingStore = otherValue
Return
End If
Dim asBinding = TryCast(otherValue, Binding)
If asBinding IsNot Nothing Then
instance.SetBinding(bindableProperty, asBinding)
Return
End If
Throw New InvalidOperationException()
ElseIf valueText.StartsWith("{") Then
If valueText.StartsWith("{Binding ") AndAlso valueText.EndsWith("}") Then
Dim propertyName = valueText.Substring(9, valueText.Length - 9 - 1)
instance.SetBinding(bindableProperty, New Binding(propertyName))
Else
Throw New FormatException(valueText)
End If
Else
backingStore = New TConverter().ConvertFromInvariantString(valueText)
End If
End Sub
Private Sub SetPropertyIfNotDefaultWithSupportForTypeConvertersAndBinding(
ByRef backingStore As String,
value As String,
valueText As String,
otherValue As Object,
instance As BindableObject,
bindableProperty As BindableProperty
)
If value IsNot Nothing AndAlso value <> valueText Then
backingStore = value
Return
ElseIf otherValue Is Nothing AndAlso valueText Is Nothing Then
backingStore = Nothing
Return
ElseIf otherValue IsNot Nothing Then
Dim asString = TryCast(otherValue, String)
If asString IsNot Nothing Then
backingStore = otherValue
Return
End If
Dim asBinding = TryCast(otherValue, Binding)
If asBinding IsNot Nothing Then
instance.SetBinding(bindableProperty, asBinding)
Return
End If
Throw New InvalidOperationException()
ElseIf valueText.StartsWith("{") Then
If valueText.StartsWith("{Binding ") AndAlso valueText.EndsWith("}") Then
Dim propertyName = valueText.Substring(9, valueText.Length - 9 - 1)
instance.SetBinding(bindableProperty, New Binding(propertyName))
Else
Throw New FormatException(valueText)
End If
Else
backingStore = valueText
End If
End Sub
Private Sub SetPropertyIfNotDefaultWithSupportForBinding(Of TValue As Structure)(
ByRef backingStore As TValue,
value As TValue,
valueText As String,
otherValue As Object,
equals As Func(Of TValue, TValue, Boolean),
defaultValueText As String,
instance As BindableObject,
bindableProperty As BindableProperty
)
If Not equals(value, Nothing) OrElse (valueText Is Nothing OrElse valueText = defaultValueText) Then
backingStore = value
Return
ElseIf otherValue IsNot Nothing Then
If TypeOf otherValue Is TValue Then
backingStore = otherValue
Return
End If
Dim asBinding = TryCast(otherValue, Binding)
If asBinding IsNot Nothing Then
instance.SetBinding(bindableProperty, asBinding)
Return
End If
Throw New InvalidOperationException()
ElseIf valueText.StartsWith("{") Then
If valueText.StartsWith("{Binding ") AndAlso valueText.EndsWith("}") Then
Dim propertyName = valueText.Substring(9, valueText.Length - 9 - 1)
instance.SetBinding(bindableProperty, New Binding(propertyName))
Else
Throw New FormatException(valueText)
End If
Else
Throw New InvalidOperationException()
End If
End Sub
#End Region
#Region " Content properties "
<Extension>
Sub SetChildContent(instance As ContentPage, content As View)
instance.Content = content
End Sub
<Extension>
Sub SetChildContent(instance As Label, content As String)
instance.Text = content
End Sub
<Extension>
Sub SetChildContent(instance As Span, content As String)
instance.Text = content
End Sub
<Extension>
Sub AddChildContent(instance As Layout(Of View), content As View)
instance.Children.Add(content)
End Sub
<Extension>
Sub AddFormattedTextChildContent(instance As Label, content As FormattedString)
instance.FormattedText = content
End Sub
<Extension>
Sub AddFormattedTextChildContent(instance As Label, content As Span)
Dim formattedString = instance.FormattedText
If formattedString Is Nothing Then
formattedString = New FormattedString
instance.FormattedText = formattedString
End If
formattedString.AddChildContent(content)
End Sub
<Extension>
Sub AddFormattedTextChildContent(instance As Label, content As String)
Dim formattedString = instance.FormattedText
If formattedString Is Nothing Then
formattedString = New FormattedString
instance.FormattedText = formattedString
End If
formattedString.AddChildContent(content)
End Sub
<Extension>
Sub AddChildContent(instance As FormattedString, content As Span)
instance.Spans.Add(content)
End Sub
<Extension>
Sub AddChildContent(instance As FormattedString, content As String)
instance.Spans.Add(New Span With {.Text = content})
End Sub
#End Region
#Region " Experimental "
<Extension>
Sub SetName(Of T As BindableObject)(instance As T, ByRef value As T, valueText As String, otherValue As Object)
value = instance
End Sub
<Extension>
Sub SetSelf(ByRef instance As ContentPage,
value As ContentPage,
valueText As String,
otherValue As Object)
instance = value
End Sub
#End Region
End Module
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