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PORestricting a WPF Textbox to integers by swallowing an exception
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  1. PORestricting a WPF Textbox to integers by swallowing an exception
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    copied!<p>I've written the following to restrict a WPF textbox to only accept integers and also only accept a number less than or equal to 35:</p> <p>In my WindowLoaded event I create a handler for 'OnPaste':</p> <pre><code>DataObject.AddPastingHandler(textBoxWorkflowCount, OnPaste); </code></pre> <p>OnPaste consists of the following:</p> <pre><code>private void OnPaste(object sender, DataObjectPastingEventArgs e) { if (!IsNumeric(e.Source.ToString(), NumberStyles.Integer)) e.Handled = true; } </code></pre> <p>and our function to force numerics only is as follows:</p> <pre><code>public bool IsNumeric(string val, NumberStyles numberStyle) { double result; return double.TryParse(val, numberStyle, CultureInfo.CurrentCulture, out result); } </code></pre> <p>The specific textbox that is having the error should also be limited to a number &lt;=35. To do this I've added the following TextChanged event: </p> <pre><code>private void TextBoxWorkflowCountTextChanged(object sender, TextChangedEventArgs e) { try { if (textBoxWorkflowCount == null || textBoxWorkflowCount.Text == string.Empty || Convert.ToInt32(textBoxWorkflowCount.Text) &lt;= 35) return; MessageBox.Show("Number of workflow errors on one submission cannot be greater then 35.", "Workflow Count too high", MessageBoxButton.OK, MessageBoxImage.Warning); textBoxWorkflowCount.Text = ""; } catch(Exception) { // todo: Oh the horror! SPAGHETTI! Must fix. Temporarily here to stop 'pasting of varchar' bug if (textBoxWorkflowCount != null) textBoxWorkflowCount.Text = ""; } } </code></pre> <p>Although this does the job and works it's very nasty/hackish and I would love to know how it could be done better for sake of improving myself... Especially so without having to swallow an exception.</p>
 

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