dotnet/aspnetcore · error · InvalidOperationException

The type '{0}' does not have an associated TypeConverter tha

Error message

The type '{0}' does not have an associated TypeConverter that supports conversion from a string. Apply 'TypeConverterAttribute' to the type to register a converter.

What it means

Thrown by BindConverter's ParserDelegateCache.MakeTypeConverterConverter when a type used in @bind has no TypeConverter capable of converting from a string. When the user edits an input, Blazor parses the DOM string back to the bound property's type; for non-primitive types it relies on TypeDescriptor.GetConverter, and if the converter cannot convert from string this InvalidOperationException is thrown. Apply [TypeConverter] with a converter supporting ConvertFrom(typeof(string)).

Source

Thrown at src/Components/Components/src/BindConverter.cs:2063

                    if (!elementParser(initialArray.GetValue(i), culture, out convertedArray[i]!))
                    {
                        value = default;
                        return false;
                    }
                }

                value = convertedArray;
                return true;
            }
        }

        [UnconditionalSuppressMessage("Trimming", "IL2026", Justification = "We expect unknown underlying types are configured by application code to be retained.")]
        private static BindParser<T> MakeTypeConverterConverter<[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.All)] T>()
        {
            var typeConverter = TypeDescriptor.GetConverter(typeof(T));
            if (typeConverter == null || !typeConverter.CanConvertFrom(typeof(string)))
            {
                throw new InvalidOperationException(
                    $"The type '{typeof(T).FullName}' does not have an associated {typeof(TypeConverter).Name} that supports " +
                    $"conversion from a string. " +
                    $"Apply '{typeof(TypeConverterAttribute).Name}' to the type to register a converter.");
            }

            return ConvertWithTypeConverter;

            bool ConvertWithTypeConverter(object? obj, CultureInfo? culture, out T value)
            {
                // We intentionally close-over the TypeConverter to cache it. The TypeDescriptor infrastructure is slow.
                if (obj == null)
                {
                    value = default!;
                    return true;
                }
                var converted = typeConverter.ConvertFrom(context: null, culture ?? CultureInfo.CurrentCulture, obj);
                if (converted == null)
                {

View on GitHub (pinned to 294cab2f9b)

Solutions

1. Create a TypeConverter subclass overriding CanConvertFrom(typeof(string)) and ConvertFrom.
2. Apply [TypeConverter(typeof(YourConverter))] to your custom type.
3. Alternatively, bind a string property and parse manually, or use a built-in type.

Example fix

// before — binding a custom type throws on parse
public struct Money { public decimal Amount; public string Currency; }

// after
[TypeConverter(typeof(MoneyConverter))]
public struct Money { public decimal Amount; public string Currency; }

public class MoneyConverter : TypeConverter
{
    public override bool CanConvertFrom(ITypeDescriptorContext c, Type t)
        => t == typeof(string) || base.CanConvertFrom(c, t);
    public override object ConvertFrom(ITypeDescriptorContext c, CultureInfo ci, object v)
        => v is string s ? new Money { Amount = decimal.Parse(s, ci) } : base.ConvertFrom(c, ci, v);
}

var converter = TypeDescriptor.GetConverter(typeof(T));
if (converter is null || !converter.CanConvertFrom(typeof(string)))
    throw new InvalidOperationException($"{typeof(T)} has no string-parsing TypeConverter.");

static bool CanParseFromString<T>()
{
    var converter = TypeDescriptor.GetConverter(typeof(T));
    return converter is not null && converter.CanConvertFrom(typeof(string));
}

When it happens

Trigger: Binding @bind to a property of a custom type without a registered TypeConverter that supports parsing strings, and the type is not among the built-in set (string, numeric, bool, DateTime, Guid, enums, arrays). The parser lookup happens at BindConverter.cs:2058-2089.

Common situations: Custom value type bound to an <input @bind=...>; binding to a record/struct used in forms; using a domain type that lacks a string round-trip converter.

Related errors

• The type '{0}' does not have an associated TypeConverter tha
• There is no file with ID ${fileId}. The file list may have c
• Invalid sequence number or identifier '${sequenceOrIdentifie
• The options parameter is required.
• The event '${eventName}' is already registered.

AI-assisted analysis of dotnet/aspnetcore@294cab2f9b (2026-08-06). Data as JSON: /api/errors/cd21203cb945d1c5. Report an issue: GitHub.