Changes

== 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.

<ctrls:EvalExpression x:Name="ExpressionEvaluatorEvaluator" Context="{Binding Self}" Expression="Context.Values[&quot;LK_OFFLINE&quot;]!=null || Context.Values[&quot;GUIDREF&quot;]!=null" /> <TextBlock Foreground="White" Visibility="{Binding ElementName=ExpressionEvaluatorEvaluator, Path=Result, Converter={StaticResource BoolToVisConverter}}" />

<ctrls:EvalExpression x:Name="ControllingVisibilityEvaluator" Context="{Binding}" Expression="Context.Values[&quot;LK_EXAMPLE&quot;]!=null || Context.Values[&quot;GUIDREF&quot;]!=null" /> <Label TextColor="#00000" IsVisible="{Binding Path=Result, Source={x:Reference ControllingVisibilityEvaluator}, Converter={StaticResource NullToBoolConverter}}" />

==== Simple Calculation calculation ====

The following example shows how to use the control an expression with three two 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 TextBlock for output in the UI.

<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}" Context="{Binding}"> <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}" />

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.

The following example shows how to use the control an expression with three two 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 a Label for output in the UI.

<Editor x:Name="Expression"/> <Editor x:Name="P0" WidthRequest="32"/> <Editor x:Name="P1" WidthRequest="43"/> <ctrls:EvalExpression x:Name="Evaluator" Expression="{Binding Path=Text, Source={x:Reference Expression}}" Context="{Binding}"> <ctrls:EvalExpressionParameter Name="P0" Value="{Binding Path=WidthRequest, Source={x:Reference P0}}" /> <ctrls:EvalExpressionParameter Name="P1" Value="{Binding Path=WidthRequest, Source={x:Reference P1}}" /> </ctrls:EvalExpression> <Label Text="{Binding Path=Result, Source={x:Reference Evaluator}}" />

Lets assume that the Since Textbox ''P0'' has a width of 32 and ''P1'' has a width of 43. If ''Expression'' now contains <code>(P0 + P1)</code> then the result would display 75.</tab>

[[Category:Client|EvalExpression]][[Category:Pages with broken file links|EvalExpression]][[Category:WinX|EvalExpression]][[Category:Xamarin|EvalExpression]] ==== Setting a calculated Property Value property value ====

<ctrls:EvalExpression x:Name="Evaluator" Expression="&quot;MP_EXAMPLE|&quot; + (P0 + 5)" Context="{Binding}"> <ctrls:EvalExpressionParameter Name="P0" Value="{Binding Values[MP_EXAMPLE], Converter={StaticResource ToType}, ConverterParameter='System.Int32'}" />

<Button Content="Tap for 5 more" Command="{Binding SetPropertyValueAndValidateCommand}" CommandParameter="{Binding ElementName=Evaluator, Path=Result}"/>

<ctrls:EvalExpression x:Name="Evaluator2Evaluator" Expression="&quot;MP_EXAMPLE|&quot; + (P0 + 2)" Context="{Binding}"> <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 Evaluator2Evaluator}}"/>

     ==== Conditional Statement statement ====

<Grid xmlns:ctrls="using:UBIK.WinX.Controls"> <ctrls:EvalExpression x:Name="InitialiseParameterWhenNull" Expression="(P0==null) ? P1 : P2" Context="{Binding}"> <Controlsctrls:EvalExpressionParameter Name="P0" Value="{Binding StoredProfileParameters[WPType1]}" /> <Controlsctrls:EvalExpressionParameter Name="P1" Value="WPType1=1" /> <Controlsctrls:EvalExpressionParameter Name="P2" Value="{Binding ElementName=InitialiseParameter, Path=Result}" /> </Controlsctrls:EvalExpression></Grid>

<controls:EvalExpression x:Name="StatusAutomatorEvaluator" 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 StatusAutomatorEvaluator}}" FontSize="16"/> </Grid>