dotnet/maui · error · InvalidOperationException

Cannot convert "{strValue}" into {typeof(FlowDirection)}

Error message

Cannot convert "{strValue}" into {typeof(FlowDirection)}

What it means

FlowDirectionConverter.ConvertFrom throws InvalidOperationException when the string is non-null but cannot be parsed as a FlowDirection enum value nor matched case-insensitively against the aliases 'ltr', 'rtl', 'inherit'. Anything else (typos, localized strings, numeric forms) is rejected.

Source

Thrown at src/Controls/src/Core/FlowDirectionConverter.cs:31

			=> destinationType == typeof(string);

		public override object? ConvertFrom(ITypeDescriptorContext? context, CultureInfo? culture, object value)
		{
			var strValue = value?.ToString();

			if (strValue != null)
			{
				if (Enum.TryParse(strValue, out FlowDirection direction))
					return direction;

				if (strValue.Equals("ltr", StringComparison.OrdinalIgnoreCase))
					return FlowDirection.LeftToRight;
				if (strValue.Equals("rtl", StringComparison.OrdinalIgnoreCase))
					return FlowDirection.RightToLeft;
				if (strValue.Equals("inherit", StringComparison.OrdinalIgnoreCase))
					return FlowDirection.MatchParent;
			}
			throw new InvalidOperationException($"Cannot convert \"{strValue}\" into {typeof(FlowDirection)}");
		}

		public override object? ConvertTo(ITypeDescriptorContext? context, CultureInfo? culture, object? value, Type destinationType)
		{
			if (value is not FlowDirection direction)
				throw new NotSupportedException();
			return direction.ToString();
		}
	}
}

View on GitHub (pinned to f377ff1c5e)

Solutions

1. Use the exact enum names (LeftToRight, RightToLeft, MatchParent) or the supported aliases 'ltr', 'rtl', 'inherit'.
2. Trim and validate the input string before assigning: `strValue?.Trim()`.
3. Provide a fallback in the binding (ConverterParameter or FallbackValue) for unknown strings.

Example fix

<!-- before -->
<Label FlowDirection="left" />

<!-- after -->
<Label FlowDirection="LeftToRight" />

var aliases = new[]{"ltr","rtl","inherit"}; var trimmed = strValue?.Trim(); if (Enum.TryParse<FlowDirection>(trimmed, out var fd) || (trimmed != null && aliases.Contains(trimmed.ToLower()))) { /* ok */ }

static bool IsValidFlowDirection(string s) => Enum.TryParse<FlowDirection>(s, out _) || s?.ToLower() is "ltr" or "rtl" or "inherit";

try { return new FlowDirectionConverter().ConvertFrom(value); } catch (InvalidOperationException) { return FlowDirection.MatchParent; }

When it happens

Trigger: Supplying a string like 'LeftToRight' (no alias match unless exact enum), 'left', 'right', 'auto', or a typo like 'ltr ' with trailing whitespace to a FlowDirection property through XAML or a converter.

Common situations: XAML authored with shorthand 'left'/'right', copy from CSS-direction semantics ('auto'), or trailing whitespace from data binding that bypasses enum parsing.

Related errors

• Cannot convert "{0}" into {1}
• throw new NotSupportedException();
• RootComponent requires a value for its Selector property, bu
• RootComponent requires a value for its ComponentType propert
• XC0040

AI-assisted analysis of dotnet/maui@f377ff1c5e (2026-08-13). Data as JSON: /api/errors/badc2040a9678582. Report an issue: GitHub.