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Editorial Team
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Asked: 2026-06-14T21:21:43+00:00

So I was asked to fix an issue with an old windows form utility

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So I was asked to fix an issue with an old windows form utility that has been around a little while (least before any of my coworkers showed up). The form has a numericUpDown control that is databound. The issue was, when you clicked the up or down arrow the values would change and save OK however, if you just typed in a number and clicked save it wouldn’t save. It was like the databinding never saw the change, so coming from a WPF background I guessed that changing the following

TaskDaysToComplete.DataBindings.Add("Value", taskTemplate, "DaysToComplete");

To this

TaskDaysToComplete.DataBindings.Add("Value", taskTemplate, "DaysToComplete", false, DataSourceUpdateMode.OnPropertyChanged);

would solve my problem and it did. You can now either type in a number or use the up/down arrows on the control to set the “Value” property.

My question is this, what was happening in the first place? I am guessing the default DataSourceUpdateMode was OnValidation but when does this happen and why was it OK for when using the up/down arrows but never seemed to happen when typing things in.

Thanks!

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1 Answer

  1. Editorial Team

    numericUD validation

    validation is done on losing focus, so when you press the up/down key the textbox loses focus – triggering the validation routine.
    when editing text you can make the control lose focus by clicking another control, this will cause it to validate.
    the reason that the default is set to onValidate is that on value changed will cause it to validate on each character typed, which can be problematic both for performance and for correct validation.

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