如何将类型转换器与配置节一起使用
本文关键字：配置 一起 转换器 类型 类型转换 | 更新日期: 2023-09-27 17:55:30
所以我有一个ConfigurationSection/ConfigurationElementCollection，它的配置是这样的：
<mimeFormats>
<add mimeFormat="text/html" />
</mimeFormats>
以下是我如何处理 mimeFormats：
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/到字符串的类型转换器？我尝试使用 MSDN 示例，但不断收到错误消息：
TypeConverter 无法从 System.String 转换。
从本质上讲，如何设置它，以便它只能与配置部分尝试执行的任何操作一起使用？
您可以将 TypeConverterAttribute 放在属性上，以告诉序列化程序如何处理它。
[TypeConverter(typeof(MimeFormatConverter))]
[ConfigurationProperty("mimeFormat", IsRequired = true)]
public MimeFormat MimeFormat
{
get { return (MimeFormat)base[_mimeFormat]; }
}
试试这个：
测试部分.cs
public class TestSection : ConfigurationSection
{
private static readonly ConfigurationProperty sFooProperty = new ConfigurationProperty("Foo",
typeof(Foo),
null,
new FooTypeConverter(),
null,
ConfigurationPropertyOptions.None);
public static readonly ConfigurationPropertyCollection sProperties = new ConfigurationPropertyCollection();
static TestSection()
{
sProperties.Add(sFooProperty);
}
public Foo Foo
{
get { return (Foo)this[sFooProperty]; }
set { this[sFooProperty] = value; }
}
protected override ConfigurationPropertyCollection Properties
{
get { return sProperties; }
}
}
傅.cs
public class Foo
{
public string First { get; set; }
public string Second { get; set; }
public override string ToString()
{
return First + ',' + Second;
}
}
FooTypeConverter.cs
public class FooTypeConverter : TypeConverter
{
public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
{
return (sourceType == typeof(string));
}
public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
{
string val = value as string;
if (val != null)
{
string[] parts = val.Split(',');
if (parts.Length != 2)
{
// Throw an exception
}
return new Foo { First = parts[0], Second = parts[1] };
}
return null;
}
public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
{
return (destinationType == typeof(string));
}
public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
{
Foo val = value as Foo;
if (val != null)
return val.ToString();
return null;
}
}
我想通了。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;
}
}
从这一点开始，您必须在 ConvertTo 和 ConvertFrom 方法中创建转换部分
public override object ConvertFrom( ITypeDescriptorContext context, CultureInfo culture, object value ) {
if ( value == null )
return null;
try {
if ( value is string ) {
string s = (string)value;
// here is where you look at the string to figure out the MimeFormat
// like so....
return new MimeFormat( s );
}
throw new NotSupportedException( NotSupportedException( value.GetType(), typeof(MimeFormat) );
}
public override object ConvertTo( ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType ) {
if ( value == null )
return null;
MimeFormat p = (MimeFormat)value;
if ( destinationType == typeof( String ) )
return p.ToString();
throw new NotSupportedException( NotSupportedException( typeof(MimeFormat), destinationType ) );
}
编辑
您还需要覆盖CanConvert函数。
public override bool CanConvertFrom( ITypeDescriptorContext context, Type sourceType ) {
if ( sourceType == typeof( string ) )
return true;
return false;
}
public override bool CanConvertTo( ITypeDescriptorContext context, Type destinationType ) {
if ( destinationType == typeof( string ) )
return true;
return false;
}