C#•12mo ago

❔ Blazor TypeConverter Exception

        [TypeConverter(typeof(IListStringConverter))]
        public List<string> AcceptedDomains { get; set; } = new List<string>()
        {
            "discord",
            "linktr.ee",
        };
    }

        [TypeConverter(typeof(IListStringConverter))]
        public List<string> AcceptedDomains { get; set; } = new List<string>()
        {
            "discord",
            "linktr.ee",
        };
    }

        <textarea placeholder="Domains" @bind=DataService.Filter.AcceptedDomains></textarea>

        <textarea placeholder="Domains" @bind=DataService.Filter.AcceptedDomains></textarea>

11 Replies

Kroks•12mo ago

The type 'System.Collections.Generic.List1[[System.String, System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]]' does not have an associated TypeConverter that supports conversion from a string. Apply 'TypeConverterAttribute' to the type to register a converter."`

 [TypeConverter(typeof(IListStringConverter))]
    public class IListStringConverter : TypeConverter
    {
        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
        {
            return sourceType == typeof(string);
        }

        public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
        {
            return destinationType == typeof(string);
        }

        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
        {
            if (value is string strValue)
            {
                string[] stringArray = strValue.Split(new[] { '\n' }, StringSplitOptions.RemoveEmptyEntries);
                return new List<string>(stringArray);
            }

            throw new NotSupportedException($"Cannot convert '{value}' to {typeof(IList<string>)}");
        }

        public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
        {
            if (value is IList<string> stringList)
            {
                return string.Join(",", stringList);
            }

            throw new NotSupportedException($"Cannot convert {typeof(IList<string>)} to '{destinationType}'");
        }
    }

 [TypeConverter(typeof(IListStringConverter))]
    public class IListStringConverter : TypeConverter
    {
        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
        {
            return sourceType == typeof(string);
        }

        public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
        {
            return destinationType == typeof(string);
        }

        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
        {
            if (value is string strValue)
            {
                string[] stringArray = strValue.Split(new[] { '\n' }, StringSplitOptions.RemoveEmptyEntries);
                return new List<string>(stringArray);
            }

            throw new NotSupportedException($"Cannot convert '{value}' to {typeof(IList<string>)}");
        }

        public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
        {
            if (value is IList<string> stringList)
            {
                return string.Join(",", stringList);
            }

            throw new NotSupportedException($"Cannot convert {typeof(IList<string>)} to '{destinationType}'");
        }
    }

IsNotNull•12mo ago

I'm not super familiar with TypeConverter, but shouldn't the destination type be List<string> instead of string? I don't think it will use IListStringConverter if it doesn't support List<string>. Your CanConvertTo will return false for List<string>.

Kroks•12mo ago

changed but still doesnt work

Kroks•12mo ago

Kroks•12mo ago

with this it works

MODiX•12mo ago

Sorry @kroks1337 your message contained blocked content and has been removed!

Kroks•12mo ago

this seems dumb

Kroks•12mo ago

also I have another issue now, the IList<string> -> string works perfect but the binded List<string> does not get updated when changing text in the text area

Kroks•12mo ago

IsNotNull•12mo ago

I am not finding documentation on using TypeConverter with Blazor, but there are a few third party articles and the GitHub issue where it was first implemented. According to the GitHub issue, you have to use TypeConverter with a class that is annotated with the TypeConverter and that overrides ToString. Inheriting from List<string> might work, but looks odd. What happens if you override ToString() on ConvertibleStringList and create the single string representation?

Accord•12mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Blazor TypeConverter Exception