如何将TypeConverters与ConfigurationSection一起使用？

Question

所以我有一个ConfigurationSection/ConfigurationElementCollection,其配置如下:

<mimeFormats>
    <add mimeFormat="text/html" />
</mimeFormats>

以下是我处理mimeFormats的方法:

 public class MimeFormatElement: ConfigurationElement
{
    #region Constructors
    /// <summary>
    /// Predefines the valid properties and prepares
    /// the property collection.
    /// </summary>
    static MimeFormatElement()
    {
        // Predefine properties here
        _mimeFormat = new ConfigurationProperty(
            "mimeFormat",
            typeof(MimeFormat),
            "*/*",
            ConfigurationPropertyOptions.IsRequired
        );
    }
    private static ConfigurationProperty _mimeFormat;
    private static ConfigurationPropertyCollection _properties;

    [ConfigurationProperty("mimeFormat", IsRequired = true)]
    public MimeFormat MimeFormat
    {
        get { return (MimeFormat)base[_mimeFormat]; }
    }
}

public class MimeFormat
{
    public string Format
    {
        get
        {
            return Type + "/" + SubType;
        }
    }
    public string Type;
    public string SubType;

    public MimeFormat(string mimeFormatStr)
    {
        var parts = mimeFormatStr.Split('/');
        if (parts.Length != 2)
        {
            throw new Exception("Invalid MimeFormat");
        }

        Type = parts[0];
        SubType = parts[1];
    }
}

显然我需要一个实际做某事的TypeConverter(而不是这个空壳):

public class MimeFormatConverter : TypeConverter
{
    public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
    {
        throw new NotImplementedException();
    }
    public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
    {
        throw new NotImplementedException();
    }

    public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
    {
        throw new NotImplementedException();
    }
    public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
    {
        throw new NotImplementedException();
    }
}

如何设置允许从/到字符串类型转换的TypeConverter？我尝试过使用MSDN示例,但我不断收到错误消息:

TypeConverter无法从System.String转换.

从本质上讲,它是如何设置的,以便它可以与ConfigurationSection尝试做的任何事情一起工作？

Answer 1

我想到了。这是解决方案：

public class MimeFormatElement: ConfigurationElement
{
    #region Constructors
    /// <summary>
    /// Predefines the valid properties and prepares
    /// the property collection.
    /// </summary>
    static MimeFormatElement()
    {
        // Predefine properties here
        _mimeFormat = new ConfigurationProperty(
            "mimeFormat",
            typeof(MimeFormat),
            "*/*",
            ConfigurationPropertyOptions.IsRequired
        );

        _properties = new ConfigurationPropertyCollection {
            _mimeFormat, _enabled
        };
    }
    private static ConfigurationProperty _mimeFormat;
    private static ConfigurationPropertyCollection _properties;

    [ConfigurationProperty("mimeFormat", IsRequired = true)]
    public MimeFormat MimeFormat
    {
        get { return (MimeFormat)base[_mimeFormat]; }
    }
}

/*******************************************/
[TypeConverter(typeof(MimeFormatConverter))]
/*******************************************/
public class MimeFormat
{
    public string Format
    {
        get
        {
            return Type + "/" + SubType;
        }
    }
    public string Type;
    public string SubType;

    public MimeFormat(string mimeFormatStr)
    {
        var parts = mimeFormatStr.Split('/');
        if (parts.Length != 2)
        {
            throw new Exception("Invalid MimeFormat");
        }

        Type = parts[0];
        SubType = parts[1];
    }
}

public class MimeFormatConverter : TypeConverter
{
    public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
    {
        return sourceType == typeof(string);
    }
    public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
    {
        return new MimeFormat((string)value);
    }

    public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
    {
        return destinationType == typeof(string);
    }
    public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
    {
        var val = (MimeFormat)value;
        return val.Type + "/" + val.SubType;
    }
}