CalculationController Controls
The CalculationController lets you describe calculations that involve numbers
in textboxes, constants and other logic. The values from these calculations can
be used in the following ways:
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Displayed on the page, whether in a Label or a textbox.
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Validators that compare numbers can evaluate the value simply by setting their
ControlIDToEvaluate property to this control's ID. Supported validators
include: CompareToValueValidator, CompareTwoFieldsValidator, RangeValidator,
and DifferenceValidator. In addition, the RequiredTextValidator can determine
if the calculation had an error.
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Like Validators, their Conditions can evaluate the value. For example, the
Enabler property on various controls use Conditions. Now those Conditions can
enable their control based on the result of a calculation.
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The calculations can include the values of other CalculationControllers on the
page. This allows reuse of a common calculation, reducing the size of the
client-side code and slightly improving performance by reducing the number of
times the code executes a calculation.
While it is typical to add together the values of textboxes to form a total,
the CalculationController can handle far more powerful expressions. Here are
the elements that you can use to develop your expressions:
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Use these textboxes: IntegerTextBox, DecimalTextBox, CurrencyTextBox, and
PercentTextBox.
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Constants (numbers)
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Subexpressions which are the same idea as putting parenthesis around an
expression to have it calculate together.
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Use any Condition object to select between two expressions. One runs if the
Condition evaluates as "success". The other, if the Condition evaluates as
"failed". This allows your expression to have different logic based on the
settings on the screen. Basically, you are developing "IF" statements.
Since the CompareToValueCondition and RangeCondition now can evaluate the
values of CalculationControllers, your IF statements can be decided by
calculations too.
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Each element – textbox, constant, subexpression, and "IF" statement – can use
these operators: add, subtract, multiply, and divide.
Here is an example of two CalculationControllers on a page, using the image
shown in design mode. They refer to three controls: two DecimalTextBoxes and a
CheckBox. The DecimalTextBoxes are used for the calculation. The CheckBox is
used for the Condition object (a CheckStateCondition):
To further refine your expressions, the CalculationController has these
features:
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The result, which is initially a decimal value, can be rounded in several ways.
It can round to a certain number of decimal places and use different rounding
rules.
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For blank textboxes, you can determine if its an error or treated as 0.
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You can supply client- and server-side functions that let you customize the
result of any element. For example, if you want the value of a textbox to be
run through the Sin() function, you write a function to use that calculation.
The CalculationController will pass you the value. Your function can report an
error for an illegal value and correct errors.
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It gracefully handles errors, such as divide by zero.
Demo 1 - The Sum of Three DecimalTextBoxes
These three DecimalTextBoxes are added together and the result is shown in a
label to the right.
This demo shows "n/a" in the Label if any of the textboxes are blank, although
you have the option to treat blank textboxes as 0 too.
A RangeValidator is assigned to the CalculationController to report an error if
the sum is not between 0 and 100. A RequiredTextValidator is assigned to the
CalculationController to report when the calculation failed (due to a blank
textbox or illegal text).
=
0.0
ASP.NET Syntax for this demo
<des:DecimalTextBox id="DecimalTextBox1"
runat="server">0</des:DecimalTextBox>
<des:DecimalTextBox id="DecimalTextBox2"
runat="server">0</des:DecimalTextBox>
<des:DecimalTextBox id="DecimalTextBox3"
runat="server">0</des:DecimalTextBox>
=
<asp:Label id="Label2" runat="server">Label</asp:Label>
<des:RequiredTextValidator id="RequiredTextValidator1" runat="server"
ControlIDToEvaluate="CalculationController1"
ErrorMessage="Please assign valid numbers to all textboxes">
<ErrorFormatterContainer>
<des:TextErrorFormatter
Display="Dynamic"></des:TextErrorFormatter>
</ErrorFormatterContainer>
</des:RequiredTextValidator>
<des:RangeValidator id="RangeValidator1" runat="server"
ControlIDToEvaluate="CalculationController1"
ErrorMessage="The total must be in the range of {MINIMUM} and {MAXIMUM}."
DataType="Double" Minimum="0" Maximum="100">
<ErrorFormatterContainer>
<des:TextErrorFormatter
Display="Dynamic"></des:TextErrorFormatter>
</ErrorFormatterContainer>
</des:RangeValidator><br>
<des:CalculationController id="CalculationController1" runat="server"
ShowValueControlID="Label1" InvalidValueLabel="n/a"
InvalidValueCssClass="DESVALErrorText"
ValidateOnCalc="True" AutoShowValue="Always">
<Expression>
<des:NumericTextBoxCalcItem BlankIsZero="False"
TextBoxControlID="DecimalTextBox1"></des:NumericTextBoxCalcItem>
<des:NumericTextBoxCalcItem BlankIsZero="False"
TextBoxControlID="DecimalTextBox2"></des:NumericTextBoxCalcItem>
<des:NumericTextBoxCalcItem BlankIsZero="False"
TextBoxControlID="DecimalTextBox3"></des:NumericTextBoxCalcItem>
</Expression>
</des:CalculationController>
Demo 2 - Using Conditional Logic
Suppose this is a checkout page where you have placed an order. You enter the
quantity, which is multiplied by the price.
In addition, you use a DropDownList to select between one of three shipping
rates.
There are 3 CalculationControllers here. The first calculates the product price
x quantity. It updates row 1.
The second row uses a CalculationController to select between several possible
prices and display its value.
The third row uses a CalculationController to add the value of the first and
second rows.
ASP.NET Syntax for this demo
<table width="500">
<tr class='TableTitles'>
<td width=200>Product name</td><td
width=100>Price</td><td width=100>Quantity</td><td
width=100>Total</td>
</tr>
<tr class="TableRows">
<td>Computer Desk #5312-30</td><td
align=right>$200.00</td>
<td><des:IntegerTextBox id="ProductQty1" runat=server Width="30px"
ShowSpinner="True" SpinnerMinValue="1" SpinnerMaxValue="99"
AllowNegatives="False">1</des:IntegerTextBox></td>
<td align=right>
<des:CalculationController id="ProductCalc1" runat=server
ShowValueControlID="ProductTotal1"
LabelFormatCurrencySymbol="True" LabelFormatThousandsSep="True"
DecimalPlaces="Currency" AutoShowValue="Always">
<Expression>
<des:ConstantCalcItem
Constant="200"></des:ConstantCalcItem>
<des:NumericTextBoxCalcItem TextBoxControlID="ProductQty1"
Operator="Multiply"></des:NumericTextBoxCalcItem>
</Expression>
</des:CalculationController>
<asp:Label ID="ProductTotal1" Runat=server></asp:Label>
</td>
</tr>
<tr class=TableRows>
<td>Shipping
<asp:DropDownList ID="ShippingDDL" Runat=server>
<asp:ListItem
Value="Overnight">Overnight</asp:ListItem>
<asp:ListItem Value="3 - 5 days">3 - 5
days</asp:ListItem>
<asp:ListItem Value="Standard Ground">Standard
Ground</asp:ListItem></asp:DropDownList></td>
<td> </td><td> </td>
<td align=right>
<des:CalculationController id="ShippingCalc" runat=server
ShowValueControlID="ShippingTotal"
LabelFormatCurrencySymbol="True" LabelFormatThousandsSep="True"
DecimalPlaces="Currency" AutoShowValue="Always">
<Expression>
<des:ConditionCalcItem>
<ConditionContainer>
<des:SelectedIndexCondition
ControlIDToEvaluate="ShippingDDL" ></des:SelectedIndexCondition>
</ConditionContainer>
<ExpressionWhenTrue>
<des:ConstantCalcItem
Constant="12.8"></des:ConstantCalcItem>
</ExpressionWhenTrue>
<ExpressionWhenFalse>
<des:ConditionCalcItem >
<ConditionContainer>
<des:SelectedIndexCondition
ControlIDToEvaluate="ShippingDDL" Index="1">
</des:SelectedIndexCondition>
</ConditionContainer>
<ExpressionWhenTrue>
<des:ConstantCalcItem
Constant="8.75"></des:ConstantCalcItem>
</ExpressionWhenTrue>
<ExpressionWhenFalse>
<des:ConstantCalcItem
Constant="4.25"></des:ConstantCalcItem>
</ExpressionWhenFalse>
</des:ConditionCalcItem>
</ExpressionWhenFalse>
</des:ConditionCalcItem>
</Expression>
</des:CalculationController>
<asp:Label ID="ShippingTotal" Runat=server></asp:Label>
</td>
</tr>
<tr><td><b>Total
Price</b></td><td> </td><td> </td>
<td align=right>
<des:CalculationController id="TotalCalc" runat=server
ShowValueControlID="PurchaseTotal"
LabelFormatCurrencySymbol="True" LabelFormatThousandsSep="True"
DecimalPlaces="Currency" AutoShowValue="Always">
<Expression>
<des:CalcControllerCalcItem
ControlID="ProductCalc1"></des:CalcControllerCalcItem>
<des:CalcControllerCalcItem
ControlID="ShippingCalc"></des:CalcControllerCalcItem>
</Expression>
</des:CalculationController>
<asp:Label ID="PurchaseTotal" Runat=server></asp:Label>
</td></tr></table>
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