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POMVVM-Light: Is this the best way to validate and revert a value in the View?
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  1. POMVVM-Light: Is this the best way to validate and revert a value in the View?
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    copied!<p>In my View I have TextBoxes like this one:</p> <pre><code>&lt;TextBox x:Name="tBoxShippingWeight" Text="{Binding ShippingWeight, Mode=TwoWay}" InputScope="Number" /&gt; </code></pre> <p>When the user enters a value I do a basic validation (not the focus of this question) and if that fails I use the System.Windows.MessageBox to notify the user of the proper params and revert the value back to the previous value, which is always valid because it either came from a default init value or was properly entered by the user. I ended up calling RaisePropertyChanged("ShippingWeight") inside the if statement that does the validation. If I put it in the catch statement, it never gets raised if the MessageBox is also called from there. Is this a reasonable way to do the reversion or is there something better? Here is the code from the ViewModel:</p> <pre><code>public string ShippingWeight { get { return ShippingModel.ShippingWeight.ToString(); } set { if (ShippingModel.ShippingWeight.ToString() == value) return; var oldValue = ShippingModel.ShippingWeight; try { int intValue = Convert.ToInt32(value); if (Convert.ToInt32(ShippingParams.ShippingWeightMin) &gt; intValue || Convert.ToInt32(ShippingParams.ShippingWeightMax) &lt; intValue) { // Revert back to previous value // NOTE: This has to be done here. If done in the catch statement, // it will never run since the MessageBox interferes with it. RaisePropertyChanged("ShippingWeight"); throw new Exception(); } ShippingModel.ShippingWeight = intValue; RaisePropertyChanged("ShippingWeight", oldValue, Convert.ToDouble(value), true); } catch (Exception) { System.Windows.MessageBox.Show("Value must be a whole number between " + ShippingParams.ShippingWeightMin + " and " + ShippingParams.ShippingWeightMax); } } </code></pre> <p>}</p>
 

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