2023-07-25T12:01:36Z

2021-01-25T11:46:29Z

LDO: /* Simple Calculation */

{{XAMLControlInfoBox
| title = {{PAGENAME}}
| name = {{PAGENAME}}
| namespace = "using:UBIK.WinX.Controls" in UBIK.UWP<br>"clr-namespace:UBIK.CPL.Controls;assembly=UBIK.CPL" in UBIK.Xamarin
| image = [[File:SY_{{PAGENAME}}.png|220px]]
| imagecaption = imagecaption
| purpose = Evaluate a C# expression in XAML
| version = 3.2+ in UBIK.UWP 1.0+ in UBIK.Xamarin
}}

== Concept==
The EvalExpression control allows to evaluate a C# expression from within XAML markup. The ''Expression'' has to be a single-line, valid C# expression ("Lambda") and has to return a single value; expressions can also reference names of subordinate [[EvalExpression#Parameters|EvalExpressionParameter]] items.

=== Examples ===
{{Hint|When writing expressions in XAML code, you have to avoid (escape) special characters. There are useful [https://www.freeformatter.com/xml-escape.html online tools] for this.}}

==== Evaluation without parameters ====
<tabs>
<tab name="UWP">
The following example shows how to evaluate a simple expression without using any parameters and then use the result for visibility binding.
<source lang = "xml">
<StackPanel xmlns:ctrls="using:UBIK.WinX.Controls">
<ctrls:EvalExpression
x:Name="ExpressionEvaluator"
Context="{Binding Self}"
Expression="Context.Values["LK_OFFLINE"]!=null || Context.Values["GUIDREF"]!=null" />
<TextBlock Foreground="White" Visibility="{Binding ElementName=ExpressionEvaluator, Path=Result, Converter={StaticResource BoolToVisConverter}}" />
</StackPanel>
</source>
The TextBlock should be visible as long as at least one of the context object's two named properties has a value.
</tab>

<tab name="Xamarin">
The following example shows how to evaluate a simple expression without using any parameters and then use the result for visibility binding.
<source lang = "xml">
<StackLayout xmlns:ctrls="clr-namespace:UBIK.CPL.Controls;assembly=UBIK.CPL">
<ctrls:EvalExpression
x:Name="ControllingVisibility"
Context="{Binding}"
Expression="Context.Values["LK_EXAMPLE"]!=null || Context.Values["GUIDREF"]!=null" />
<Label
TextColor="#00000"
IsVisible="{Binding Path=Result, Source={x:Reference ControllingVisibility}, Converter={StaticResource NullToBoolConverter}}" />
</StackLayout>
</source>
The Label should be visible as long as at least one of the context object's two named properties has a value.</tab>
</tabs>

==== Simple Calculation ====
<tabs>
<tab name="UWP">
The following example shows how to use the control with three parameters, where the first two are user input (Textbox ''Param0'' and ''Param1'') and the third one is a property from its DataContext (ViewModel). The evaluated ''Result'' is then bound to a Textblock for output in the UI.
<source lang = "xml">
<StackPanel xmlns:ctrls="using:UBIK.WinX.Controls"
HorizontalAlignment="Center"
Orientation="Vertical">
<TextBox x:Name="Expression" Width="200" />
<TextBox x:Name="Param0" Width="200" />
<TextBox x:Name="Param1" Width="200" />
<ctrls:EvalExpression x:Name="Evaluator" Expression="{Binding ElementName=Expression, Path=Text}">
<ctrls:EvalExpressionParameter Name="P0" Value="{Binding ElementName=Param0, Path=Text, Converter={StaticResource ToType}, ConverterParameter='System.Int32'}" />
<ctrls:EvalExpressionParameter Name="P1" Value="{Binding ElementName=Param1, Path=Text, Converter={StaticResource ToType}, ConverterParameter='System.Int32'}" />
<ctrls:EvalExpressionParameter Name="P2" Value="{Binding IsLoggedIn}" />
</ctrls:EvalExpression>
<TextBlock Foreground="White" Text="{Binding ElementName=Evaluator, Path=Result}" />
</StackPanel>
</source>
Lets assume that the Textbox ''Param0'' contains a text of 42 and ''Param1'' contains a text of 43. If ''Expression'' now contains <code>(P0 + P1) *2</code> then the result would display 170.
</tab>

<tab name="Xamarin -> example under construction">
The following example shows how to use the control with three parameters, where the first two are user input (Editor ''Param0'' and ''Param1'') and the third one is a property from its DataContext (ViewModel). The evaluated ''Result'' is then bound to an Label for output in the UI.
<source lang = "xml">
<StackLayout xmlns:ctrls="clr-namespace:UBIK.CPL.Controls;assembly=UBIK.CPL">
<Editor x:Name="Expression"/>
<Editor x:Name="Param0" Width="32"/>
<Editor x:Name="Param1" Width="43"/>
<ctrls:EvalExpression x:Name="Evaluator" Expression="{Binding Path=Text, Source={x:Reference Expression}}">
<ctrls:EvalExpressionParameter Name="P0" Value="{Binding Path=Width, Source={x:Reference Param0}}" />
<ctrls:EvalExpressionParameter Name="P1" Value="{Binding Path=Width, Source={x:Reference Param1}}" />
</ctrls:EvalExpression>
<Label Text="{Binding Path=Result, Source={x:Reference Evaluator}}" />
</StackLayout>
</source>
Lets assume that the Textbox ''Param0''has a width of 32 and ''Param1'' has a width of 43. If ''Expression'' now contains <code>(P0 + P1) *2</code> then the result would display 75.</tab>
</tabs>

[[Category:Client|EvalExpression]]
[[Category:Pages with broken file links|EvalExpression]]
[[Category:WinX|EvalExpression]]
[[Category:Xamarin|EvalExpression]]

==== Setting a calculated Property Value ====
<tabs>
<tab name="UWP">
The following example shows how to create a button that adds and stores +5 to the value of a a numeric property named ''MP_EXAMPLE'', every time it is pressed:
<source lang = "xml">
<Grid xmlns:ctrls="using:UBIK.WinX.Controls">
<ctrls:EvalExpression x:Name="Evaluator" Expression=""MP_EXAMPLE|" + (P0 + 5)">
<ctrls:EvalExpressionParameter Name="P0" Value="{Binding Values[MP_EXAMPLE], Converter={StaticResource ToType}, ConverterParameter='System.Int32'}" />
</ctrls:EvalExpression>
<Button Content="Tap for 5 more" Command="{Binding SetPropertyValueAndValidateCommand}" CommandParameter="{Binding ElementName=Evaluator, Path=Result}"/>
</Grid>
</source>
</tab>

<tab name="Xamarin">
The following example shows how to create a button that adds and stores +5 to the value of a a numeric property named ''MP_EXAMPLE'', every time it is pressed:
<source lang = "xml">
<Grid xmlns:ctrls="clr-namespace:UBIK.CPL.Controls;assembly=UBIK.CPL">
<ctrls:EvalExpression x:Name="Evaluator2" Expression=""MP_EXAMPLE|" + (P0 + 2)">
<ctrls:EvalExpressionParameter Name="P0" Value="{Binding Values[MP_EXAMPLE]}" />
</ctrls:EvalExpression>
<Button Text="Tap to add 2 more"
Command="{Binding SetPropertyValueAndValidateCommand}" CommandParameter="{Binding Path=Result, Source={x:Reference Evaluator2}}"/>
</Grid>
</source>
</tab>
</tabs>

== Conditional Statement ==
<tabs>
<tab name="UWP">
If / Or statements can be evaluated using the C# syntax P0 ? P1 : P2.
In this case, if the result of the P0 expression is True, P1 will be effected. Otherwise, P2 will be.
<source lang = "xml">
<Controls:EvalExpression x:Name="InitialiseParameterWhenNull" Expression="(P0==null) ? P1 : P2">
<Controls:EvalExpressionParameter Name="P0" Value="{Binding StoredProfileParameters[WPType1]}" />
<Controls:EvalExpressionParameter Name="P1" Value="WPType1=1" />
<Controls:EvalExpressionParameter Name="P2" Value="{Binding ElementName=InitialiseParameter, Path=Result}" />
</Controls:EvalExpression>
</source>
</tab>

<tab name="Xamarin">
If / Or statements can also be evaluated using various C# syntax.
In this case, if the result of the P0 expression is true P00 will be used, if P1 is true P10 will be used.
<source lang = "xml">
<Grid xmlns:ctrls="clr-namespace:UBIK.CPL.Controls;assembly=UBIK.CPL">
<controls:EvalExpression x:Name="StatusAutomator" Expression="P0 == true ? P00 : (P1 == true ? P10)" Context="{Binding}">
<controls:EvalExpressionParameter Name="P0" Value="{Binding Values[MP_STATUS], Converter={StaticResource EqualityToBool}, ConverterParameter=0}" />
<controls:EvalExpressionParameter Name="P00" Value="State1" />
<controls:EvalExpressionParameter Name="P1" Value="{Binding Values[MP_STATUS], Converter={StaticResource EqualityToBool}, ConverterParameter=10}" />
<controls:EvalExpressionParameter Name="P10" Value="State2" />
</controls:EvalExpression>
<Label
Text="{Binding Path=Result, Source={x:Reference StatusAutomator}}"
FontSize="16"/>
</Grid>
</source>
</tab>
</tabs>

== Parameters ==
EvalExpressionParameters can be added as child objects to an EvalExpression control. Each parameter object needs a unique ''Name'' and a ''Value'', where the latter can be either a constant or dynamic value supplied through a binding.

==See also==
* [[XAML]]

[[Category:Client|EvalExpression]]
[[Category:Pages with broken file links|EvalExpression]]
[[Category:WinX|EvalExpression]]
[[Category:Xamarin|EvalExpression]]

EvalExpression

2021-01-25T11:45:27Z

LDO: /* Simple Calculation */

{{XAMLControlInfoBox
| title = {{PAGENAME}}
| name = {{PAGENAME}}
| namespace = "using:UBIK.WinX.Controls" in UBIK.UWP<br>"clr-namespace:UBIK.CPL.Controls;assembly=UBIK.CPL" in UBIK.Xamarin
| image = [[File:SY_{{PAGENAME}}.png|220px]]
| imagecaption = imagecaption
| purpose = Evaluate a C# expression in XAML
| version = 3.2+ in UBIK.UWP 1.0+ in UBIK.Xamarin
}}

== Concept==
The EvalExpression control allows to evaluate a C# expression from within XAML markup. The ''Expression'' has to be a single-line, valid C# expression ("Lambda") and has to return a single value; expressions can also reference names of subordinate [[EvalExpression#Parameters|EvalExpressionParameter]] items.

=== Examples ===
{{Hint|When writing expressions in XAML code, you have to avoid (escape) special characters. There are useful [https://www.freeformatter.com/xml-escape.html online tools] for this.}}

==== Evaluation without parameters ====
<tabs>
<tab name="UWP">
The following example shows how to evaluate a simple expression without using any parameters and then use the result for visibility binding.
<source lang = "xml">
<StackPanel xmlns:ctrls="using:UBIK.WinX.Controls">
<ctrls:EvalExpression
x:Name="ExpressionEvaluator"
Context="{Binding Self}"
Expression="Context.Values["LK_OFFLINE"]!=null || Context.Values["GUIDREF"]!=null" />
<TextBlock Foreground="White" Visibility="{Binding ElementName=ExpressionEvaluator, Path=Result, Converter={StaticResource BoolToVisConverter}}" />
</StackPanel>
</source>
The TextBlock should be visible as long as at least one of the context object's two named properties has a value.
</tab>

<tab name="Xamarin">
The following example shows how to evaluate a simple expression without using any parameters and then use the result for visibility binding.
<source lang = "xml">
<StackLayout xmlns:ctrls="clr-namespace:UBIK.CPL.Controls;assembly=UBIK.CPL">
<ctrls:EvalExpression
x:Name="ControllingVisibility"
Context="{Binding}"
Expression="Context.Values["LK_EXAMPLE"]!=null || Context.Values["GUIDREF"]!=null" />
<Label
TextColor="#00000"
IsVisible="{Binding Path=Result, Source={x:Reference ControllingVisibility}, Converter={StaticResource NullToBoolConverter}}" />
</StackLayout>
</source>
The Label should be visible as long as at least one of the context object's two named properties has a value.</tab>
</tabs>

==== Simple Calculation ====
<tabs>
<tab name="UWP">
The following example shows how to use the control with three parameters, where the first two are user input (Textbox ''Param0'' and ''Param1'') and the third one is a property from its DataContext (ViewModel). The evaluated ''Result'' is then bound to a Textblock for output in the UI.
<source lang = "xml">
<StackPanel xmlns:ctrls="using:UBIK.WinX.Controls"
HorizontalAlignment="Center"
Orientation="Vertical">
<TextBox x:Name="Expression" Width="200" />
<TextBox x:Name="Param0" Width="200" />
<TextBox x:Name="Param1" Width="200" />
<ctrls:EvalExpression x:Name="Evaluator" Expression="{Binding ElementName=Expression, Path=Text}">
<ctrls:EvalExpressionParameter Name="P0" Value="{Binding ElementName=Param0, Path=Text, Converter={StaticResource ToType}, ConverterParameter='System.Int32'}" />
<ctrls:EvalExpressionParameter Name="P1" Value="{Binding ElementName=Param1, Path=Text, Converter={StaticResource ToType}, ConverterParameter='System.Int32'}" />
<ctrls:EvalExpressionParameter Name="P2" Value="{Binding IsLoggedIn}" />
</ctrls:EvalExpression>
<TextBlock Foreground="White" Text="{Binding ElementName=Evaluator, Path=Result}" />
</StackPanel>
</source>
Lets assume that the Textbox ''Param0'' contains a text of 42 and ''Param1'' contains a text of 43. If ''Expression'' now contains <code>(P0 + P1) *2</code> then the result would display 170.
</tab>

<tab name="Xamarin">
The following example shows how to use the control with three parameters, where the first two are user input (Editor ''Param0'' and ''Param1'') and the third one is a property from its DataContext (ViewModel). The evaluated ''Result'' is then bound to an Label for output in the UI.
<source lang = "xml">
<StackLayout xmlns:ctrls="clr-namespace:UBIK.CPL.Controls;assembly=UBIK.CPL">
<Editor x:Name="Expression"/>
<Editor x:Name="Param0" Width="32"/>
<Editor x:Name="Param1" Width="43"/>
<ctrls:EvalExpression x:Name="Evaluator" Expression="{Binding Path=Text, Source={x:Reference Expression}}">
<ctrls:EvalExpressionParameter Name="P0" Value="{Binding Path=Width, Source={x:Reference Param0}}" />
<ctrls:EvalExpressionParameter Name="P1" Value="{Binding Path=Width, Source={x:Reference Param1}}" />
</ctrls:EvalExpression>
<Label Text="{Binding Path=Result, Source={x:Reference Evaluator}}" />
</StackLayout>
</source>
Lets assume that the Textbox ''Param0''has a width of 32 and ''Param1'' has a width of 43. If ''Expression'' now contains <code>(P0 + P1) *2</code> then the result would display 75.</tab>
</tabs>

[[Category:Client|EvalExpression]]
[[Category:Pages with broken file links|EvalExpression]]
[[Category:WinX|EvalExpression]]
[[Category:Xamarin|EvalExpression]]

==== Setting a calculated Property Value ====
<tabs>
<tab name="UWP">
The following example shows how to create a button that adds and stores +5 to the value of a a numeric property named ''MP_EXAMPLE'', every time it is pressed:
<source lang = "xml">
<Grid xmlns:ctrls="using:UBIK.WinX.Controls">
<ctrls:EvalExpression x:Name="Evaluator" Expression=""MP_EXAMPLE|" + (P0 + 5)">
<ctrls:EvalExpressionParameter Name="P0" Value="{Binding Values[MP_EXAMPLE], Converter={StaticResource ToType}, ConverterParameter='System.Int32'}" />
</ctrls:EvalExpression>
<Button Content="Tap for 5 more" Command="{Binding SetPropertyValueAndValidateCommand}" CommandParameter="{Binding ElementName=Evaluator, Path=Result}"/>
</Grid>
</source>
</tab>

<tab name="Xamarin">
The following example shows how to create a button that adds and stores +5 to the value of a a numeric property named ''MP_EXAMPLE'', every time it is pressed:
<source lang = "xml">
<Grid xmlns:ctrls="clr-namespace:UBIK.CPL.Controls;assembly=UBIK.CPL">
<ctrls:EvalExpression x:Name="Evaluator2" Expression=""MP_EXAMPLE|" + (P0 + 2)">
<ctrls:EvalExpressionParameter Name="P0" Value="{Binding Values[MP_EXAMPLE]}" />
</ctrls:EvalExpression>
<Button Text="Tap to add 2 more"
Command="{Binding SetPropertyValueAndValidateCommand}" CommandParameter="{Binding Path=Result, Source={x:Reference Evaluator2}}"/>
</Grid>
</source>
</tab>
</tabs>

== Conditional Statement ==
<tabs>
<tab name="UWP">
If / Or statements can be evaluated using the C# syntax P0 ? P1 : P2.
In this case, if the result of the P0 expression is True, P1 will be effected. Otherwise, P2 will be.
<source lang = "xml">
<Controls:EvalExpression x:Name="InitialiseParameterWhenNull" Expression="(P0==null) ? P1 : P2">
<Controls:EvalExpressionParameter Name="P0" Value="{Binding StoredProfileParameters[WPType1]}" />
<Controls:EvalExpressionParameter Name="P1" Value="WPType1=1" />
<Controls:EvalExpressionParameter Name="P2" Value="{Binding ElementName=InitialiseParameter, Path=Result}" />
</Controls:EvalExpression>
</source>
</tab>

<tab name="Xamarin">
If / Or statements can also be evaluated using various C# syntax.
In this case, if the result of the P0 expression is true P00 will be used, if P1 is true P10 will be used.
<source lang = "xml">
<Grid xmlns:ctrls="clr-namespace:UBIK.CPL.Controls;assembly=UBIK.CPL">
<controls:EvalExpression x:Name="StatusAutomator" Expression="P0 == true ? P00 : (P1 == true ? P10)" Context="{Binding}">
<controls:EvalExpressionParameter Name="P0" Value="{Binding Values[MP_STATUS], Converter={StaticResource EqualityToBool}, ConverterParameter=0}" />
<controls:EvalExpressionParameter Name="P00" Value="State1" />
<controls:EvalExpressionParameter Name="P1" Value="{Binding Values[MP_STATUS], Converter={StaticResource EqualityToBool}, ConverterParameter=10}" />
<controls:EvalExpressionParameter Name="P10" Value="State2" />
</controls:EvalExpression>
<Label
Text="{Binding Path=Result, Source={x:Reference StatusAutomator}}"
FontSize="16"/>
</Grid>
</source>
</tab>
</tabs>

== Parameters ==
EvalExpressionParameters can be added as child objects to an EvalExpression control. Each parameter object needs a unique ''Name'' and a ''Value'', where the latter can be either a constant or dynamic value supplied through a binding.

==See also==
* [[XAML]]

[[Category:Client|EvalExpression]]
[[Category:Pages with broken file links|EvalExpression]]
[[Category:WinX|EvalExpression]]
[[Category:Xamarin|EvalExpression]]