dotnet/wpf · error · ArgumentException

' ' is not a valid value for this control.

Error message

'{0}' is not a valid value for this control.

What it means

The Win32 edit box proxy throws ArgumentException(NotAValidValue) from IValueProvider.SetValue when the control has the ES_NUMBER style but the supplied string contains alphabetic characters. A numeric-only edit control cannot accept non-numeric text.

Solutions

1. Strip or validate the string so it contains only numeric characters before calling SetValue.
2. Pass the number formatted as digits only, e.g. value.ToString(CultureInfo.InvariantCulture).
3. If non-numeric text is genuinely needed, recreate the edit control without ES_NUMBER.
4. Catch ArgumentException and surface a clear 'numeric field' validation message to the user.

Example fix

// before
valuePattern.SetValue("12 items"); // ArgumentException: not a valid value
// after
string numeric = new string(raw.Where(char.IsDigit).ToArray());
if (numeric.Length > 0) valuePattern.SetValue(numeric);

if (raw.Any(char.IsLetter))
    throw new ArgumentException("Numeric field requires digits only");
valuePattern.SetValue(raw);

try { vp.SetValue(s); }
catch (ArgumentException) { /* reject non-numeric input upstream */ }

When it happens

Trigger: Calling IValueProvider.SetValue on a WindowsEditBox whose window styles include ES_NUMBER, with a string containing any letter (char.IsLetter).

Common situations: Automating numeric input fields (age, quantity, port) and passing formatted values like '12abc', 'N/A', or values with letters from a spreadsheet; localized number formatting carrying letter suffixes.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• Operation cannot be performed.
• throw new…
• Value is read-only.
• Buffer size is too small to accommodate the specified…
• Cannot have leading path delimiter.

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/a40b49b4cd190d33. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/UIAutomation/UIAutomationClientSideProviders/MS/Internal/AutomationProxies/WindowsEditBox.cs:282

            // Ensure that the edit box and all its parents are enabled.
            Misc.CheckEnabled(_hwnd);

            int styles = WindowStyle;

            if (Misc.IsBitSet(styles, NativeMethods.ES_READONLY))
            {
                throw new InvalidOperationException(SR.ValueReadonly);
            }

            // check if control only accepts numbers
            if (Misc.IsBitSet(styles, NativeMethods.ES_NUMBER))
            {
                // check if string contains any non-numeric characters.
                foreach (char ch in str)
                {
                    if (char.IsLetter (ch))
                    {
                        throw new ArgumentException(SR.Format(SR.NotAValidValue, str), "val");
                    }
                }
            }

            // Text/edit box should not enter more characters than what is allowed through keyboard.
            // Determine the max number of chars this editbox accepts
            int result = Misc.ProxySendMessageInt(_hwnd, NativeMethods.EM_GETLIMITTEXT, IntPtr.Zero, IntPtr.Zero);
            // A result of -1 means that no limit is set.
            if (result != -1 && result < str.Length)
            {
                throw new InvalidOperationException (SR.OperationCannotBePerformed);
            }

            // Send the message...
            result = Misc.ProxySendMessageInt(_hwnd, NativeMethods.WM_SETTEXT, IntPtr.Zero, new StringBuilder(str));
            if (result != 1)
            {
                throw new InvalidOperationException(SR.OperationCannotBePerformed);

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