dotnet/maui · error · InvalidOperationException

Cannot convert null into {typeof(ButtonContentLayout)}

Error message

Cannot convert null into {typeof(ButtonContentLayout)}

What it means

Thrown by ButtonContentLayoutTypeConverter.ConvertFrom when value?.ToString() returns null. The converter can only parse string representations of a ButtonContentLayout (e.g. the content layout XAML attribute); a null input has no string form and cannot be converted.

Source

Thrown at src/Controls/src/Core/Button/Button.cs:585

		}

		/// <summary>
		/// A converter to convert a string to a <see cref="ButtonContentLayout"/> object.
		/// </summary>
		public sealed class ButtonContentTypeConverter : TypeConverter
		{
			public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
				=> sourceType == typeof(string);

			public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
				=> false;

			public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
			{
				// IMPORTANT! Update ButtonContentDesignTypeConverter.IsValid if making changes here
				var strValue = value?.ToString();
				if (strValue == null)
					throw new InvalidOperationException($"Cannot convert null into {typeof(ButtonContentLayout)}");

				string[] parts = strValue.Split(new[] { ',' }, StringSplitOptions.RemoveEmptyEntries);

				if (parts.Length != 1 && parts.Length != 2)
					throw new InvalidOperationException($"Cannot convert \"{strValue}\" into {typeof(ButtonContentLayout)}");

				double spacing = DefaultSpacing;
				var position = ButtonContentLayout.ImagePosition.Left;

				var spacingFirst = char.IsDigit(parts[0][0]);

				int positionIndex = spacingFirst ? (parts.Length == 2 ? 1 : -1) : 0;
				int spacingIndex = spacingFirst ? 0 : (parts.Length == 2 ? 1 : -1);

				if (spacingIndex > -1)
					spacing = double.Parse(parts[spacingIndex], CultureInfo.InvariantCulture);

				if (positionIndex > -1)

View on GitHub (pinned to f377ff1c5e)

Solutions

1. Provide a non-null string value in the format expected (e.g. "Left,10" or "Top").
2. Guard the source so it never evaluates to null before it reaches the converter.
3. Use a fallback/default ButtonContentLayout instance instead of null.

Example fix

// before
button.ContentLayout = (ButtonContentLayout)
    new ButtonContentTypeConverter().ConvertFrom(null, culture, null);

// after
button.ContentLayout = new ButtonContentLayout(ButtonContentLayout.ImagePosition.Left, 10);

if (value is null) return new ButtonContentLayout(ButtonContentLayout.ImagePosition.Left, ButtonContentLayout.DefaultSpacing);
// otherwise proceed with converter

static bool CanConvertToButtonContentLayout(object v) =>
    v is string s && !string.IsNullOrWhiteSpace(s);

When it happens

Trigger: Passing null to the converter. A XAML attribute resolving to null (binding evaluates to null, or a StaticResource missing). Programmatic TypeConverter.ConvertFrom(null) invocation.

Common situations: Binding the ContentLayout property to a source whose value becomes null. XAML with a missing/empty attribute routed through the converter. Serialization round-trips that lose the value.

Related errors

• Cannot convert "{strValue}" into {typeof(ButtonContentLayout
• Cannot convert "{0}" into {1}
• XC0040
• XC0040
• XC0040

AI-assisted analysis of dotnet/maui@f377ff1c5e (2026-08-13). Data as JSON: /api/errors/f20aeda5333d4efa. Report an issue: GitHub.