我正在使用 PropertyGrid 控件来编辑我的应用程序中的一些对象。我正在使用自定义 TypeConverter 和 TypeEditors 以获得更好的用户界面。
我对 bool 属性的自定义 TypeConverter 有疑问。如果我有这门课:
public class MyClass {
public string Name { get; set; }
[System.ComponentModel.TypeConverter( typeof( BoolTypeConverter ) )]
public bool Flag { get; set; }
}
然后我创建实例并将其设置为 PropertyGrid 中的 SelectedObject - 一切都很好,直到用户双击属性网格项形成“Flag”属性。在 DoubleClick 引发此消息后:
(来源:tcks.wz.cz)
TypeConverter 类看起来:
public class BoolTypeConverter : System.ComponentModel.TypeConverter {
public const string TEXT_TRUE = "On";
public const string TEXT_FALSE = "Off";
public const string TEXT_NONE = "< none >";
public override object CreateInstance( System.ComponentModel.ITypeDescriptorContext context, System.Collections.IDictionary propertyValues ) {
object ret = base.CreateInstance( context, propertyValues );
return ret;
}
public override bool GetCreateInstanceSupported( System.ComponentModel.ITypeDescriptorContext context ) {
bool ret = base.GetCreateInstanceSupported( context );
return ret;
}
public override bool IsValid( System.ComponentModel.ITypeDescriptorContext context, object value ) {
bool ret;
if ( value is string ) {
string tmpValue = value.ToString().Trim();
if ( string.Compare( tmpValue, TEXT_NONE, StringComparison.InvariantCultureIgnoreCase ) == 0 ) {
ret = true;
}
else if ( string.Compare( tmpValue, TEXT_TRUE, StringComparison.InvariantCultureIgnoreCase ) == 0 ) {
ret = true;
}
else if ( string.Compare( tmpValue, TEXT_FALSE, StringComparison.InvariantCultureIgnoreCase ) == 0 ) {
ret = true;
}
else {
bool blValue;
ret = bool.TryParse( tmpValue, out blValue );
}
}
else {
ret = base.IsValid( context, value );
}
return ret;
}
public override bool CanConvertFrom( System.ComponentModel.ITypeDescriptorContext context, Type sourceType ) {
bool ret = false;
if ( sourceType == typeof( string ) ) {
ret = true;
}
else {
ret = base.CanConvertFrom( context, sourceType );
}
return ret;
}
public override object ConvertFrom( System.ComponentModel.ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value ) {
object ret = null;
bool converted = false;
if ( value is string ) {
string tmpValue = value.ToString().Trim();
if ( string.Compare( tmpValue, TEXT_NONE, StringComparison.InvariantCultureIgnoreCase ) == 0
|| string.IsNullOrEmpty( tmpValue ) ) {
ret = null;
converted = true;
}
else if ( string.Compare( tmpValue, TEXT_TRUE, StringComparison.InvariantCultureIgnoreCase ) == 0 ) {
ret = true;
converted = true;
}
else if ( string.Compare( tmpValue, TEXT_FALSE, StringComparison.InvariantCultureIgnoreCase ) == 0 ) {
ret = false;
converted = true;
}
else {
bool blValue;
if ( converted = bool.TryParse( tmpValue, out blValue ) ) {
ret = blValue;
}
}
}
if ( false == converted ) {
ret = base.ConvertFrom( context, culture, value );
}
return ret;
}
public override bool CanConvertTo( System.ComponentModel.ITypeDescriptorContext context, Type destinationType ) {
bool ret = false;
if ( destinationType == typeof( bool ) ) {
ret = true;
}
else {
ret = base.CanConvertTo( context, destinationType );
}
return ret;
}
public override object ConvertTo( System.ComponentModel.ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value, Type destinationType ) {
object ret = null;
bool converted = false;
if ( destinationType == typeof( string ) ) {
if ( null == value ) {
ret = TEXT_NONE;
converted = true;
}
else if ( value is bool? || value is bool ) {
if ( (bool)value ) { ret = TEXT_TRUE; }
else { ret = TEXT_FALSE; }
converted = true;
}
else if ( value is string ) {
ret = value;
converted = true;
}
}
if ( false == converted ) {
ret = base.ConvertTo( context, culture, value, destinationType );
}
return ret;
}
public override StandardValuesCollection GetStandardValues( System.ComponentModel.ITypeDescriptorContext context ) {
StandardValuesCollection ret;
Type tpProperty = context.PropertyDescriptor.PropertyType;
if ( tpProperty == typeof( bool ) ) {
ret = new StandardValuesCollection( new string[]{
TEXT_TRUE, TEXT_FALSE
} );
}
else if ( tpProperty == typeof( bool? ) ) {
ret = new StandardValuesCollection( new string[]{
TEXT_TRUE, TEXT_FALSE, TEXT_NONE
} );
}
else {
ret = new StandardValuesCollection( new string[0] );
}
return ret;
}
public override bool GetStandardValuesSupported( System.ComponentModel.ITypeDescriptorContext context ) {
bool ret;
Type tpProperty = context.PropertyDescriptor.PropertyType;
if ( tpProperty == typeof( bool ) || tpProperty == typeof( bool? ) ) {
ret = true;
}
else {
ret = false;
}
return ret;
}
}
这种行为让用户非常困惑。我该如何预防?
谢谢
最佳答案
您的 GetStandardValues() 方法有误。它必须返回属性类型,而不是字符串:
public override StandardValuesCollection GetStandardValues(ITypeDescriptorContext context)
{
StandardValuesCollection ret;
Type tpProperty = context.PropertyDescriptor.PropertyType;
if (tpProperty == typeof(bool))
ret = new StandardValuesCollection(new object[] { true, false });
else if (tpProperty == typeof(bool?))
ret = new StandardValuesCollection(new object[] { true, false, null });
else
ret = new StandardValuesCollection(new object[0]);
return ret;
}
关于c# - 属性网格项和 DoubleClick,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/2362535/