dotnet/wpf · error · ArgumentException

SR.Format(SR.NotAValidValue, str)

Error message

SR.Format(SR.NotAValidValue, str)

What it means

When a rich edit control has the ES_NUMBER style, SetValue validates that the new string contains no alphabetic characters before sending it. A string containing letters is not a valid numeric value for that control, so it throws ArgumentException(SR.Format(SR.NotAValidValue, str)) with parameter name "val".

Solutions

  1. Strip or correct non-numeric characters before calling SetValue on ES_NUMBER fields
  2. Use char.IsLetter checks in your own pre-validation to reject bad input early
  3. If the field must accept non-numeric text, change the control style (remove ES_NUMBER) in the target app
  4. Parse the numeric portion (e.g. double.TryParse) and set only the numeric string

Example fix

// before
valuePattern.SetValue("12 kg"); // ArgumentException: NotAValidValue
// after
string numeric = new string(text.Where(c => !char.IsLetter(c)).ToArray());
if (!string.IsNullOrWhiteSpace(numeric))
    valuePattern.SetValue(numeric);
Defensive patterns

Strategy: validation

Validate before calling

bool IsNumericSafeForEsNumber(string s) => !s.Any(char.IsLetter);

Type guard

bool IsNumericText(string s) => s.All(c => !char.IsLetter(c));

Try / catch

try { valuePattern.SetValue(val); } catch (ArgumentException) { /* value contains letters on an ES_NUMBER field */ }

Prevention

When it happens

Trigger: Calling ValuePattern.SetValue(str) on an ES_NUMBER-styled rich edit with a string containing any letter (e.g. "12a4").

Common situations: Automation feeding unvalidated user input or formatted strings ("12 kg", "1.5x") into numeric-only fields; locale-specific digit/letter characters sneaking into values.

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

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/43f283dccec1a0d8. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/UIAutomation/UIAutomationClientSideProviders/MS/Internal/AutomationProxies/WindowsRichEdit.cs:180

            if (!SafeNativeMethods.IsWindowEnabled(_hwnd))
            {
                throw new ElementNotEnabledException();
            }

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

            // check if control only accepts numbers
            if (Misc.IsBitSet(WindowStyle, NativeMethods.ES_NUMBER) && !WindowsFormsHelper.IsWindowsFormsControl(_hwnd))
            {
                // 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);
            if (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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