98 lines
3.7 KiB
C#
98 lines
3.7 KiB
C#
using System;
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using System.Collections.Generic;
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using System.ComponentModel;
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using System.Linq;
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namespace DynamicDescriptors;
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/// <summary>
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/// A <see cref="StringConverter"/> that provides a collection of standard values.
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/// </summary>
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public sealed class StandardValuesStringConverter : StringConverter
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{
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/// <summary>
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/// An empty StandardValuesCollection, to be returned when the values factory is not populated.
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/// </summary>
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private static readonly StandardValuesCollection EmptyStandardValuesCollection = new StandardValuesCollection(new string[] { });
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/// <summary>
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/// A factory that supplies the standard values to be supported.
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/// </summary>
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private readonly Func<string[]> _valuesFactory;
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/// <summary>
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/// Initializes a new instance of the <see cref="StandardValuesStringConverter"/> class.
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/// </summary>
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/// <param name="values">
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/// An enumerator that iterates through the sequence of standard values to be supported.
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/// </param>
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public StandardValuesStringConverter(IEnumerable<string> values)
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{
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_valuesFactory = values != null
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? () => values.ToArray()
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: null;
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}
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/// <summary>
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/// Initializes a new instance of the <see cref="StandardValuesStringConverter"/> class.
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/// </summary>
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/// <param name="valuesFactory">A function that supplies the standard values to be supported.</param>
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public StandardValuesStringConverter(Func<string[]> valuesFactory)
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{
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_valuesFactory = valuesFactory;
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}
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/// <summary>
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/// Returns a value indicating whether this object supports a standard set of values that
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/// can be picked from a list, using the specified context.
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/// </summary>
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/// <param name="context">
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/// An <see cref="ITypeDescriptorContext"/> that provides a format context.
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/// </param>
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/// <returns>
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/// true if <see cref="TypeConverter.GetStandardValues()"/> should be called to
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/// find a common set of values the object supports; otherwise, false.
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/// </returns>
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public override bool GetStandardValuesSupported(ITypeDescriptorContext context)
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{
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return true;
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}
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/// <summary>
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/// Returns whether the collection of standard values returned from
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/// <see cref="TypeConverter.GetStandardValues()"/> is an exclusive list of
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/// possible values, using the specified context.
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/// </summary>
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/// <param name="context">
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/// An <see cref="ITypeDescriptorContext"/> that provides a format context.
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/// </param>
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/// <returns>
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/// true if the <see cref="TypeConverter.StandardValuesCollection"/> returned from
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/// <see cref="TypeConverter.GetStandardValues()"/> is an exhaustive list of
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/// possible values; false if other values are possible.
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/// </returns>
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public override bool GetStandardValuesExclusive(ITypeDescriptorContext context)
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{
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return true;
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}
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/// <summary>
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/// Returns a collection of standard string values.
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/// </summary>
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/// <param name="context">
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/// An <see cref="ITypeDescriptorContext"/> that provides a format context that
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/// can be used to extract additional information about the environment from which this
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/// converter is invoked. This parameter or properties of this parameter can be null.
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/// </param>
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/// <returns>
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/// A <see cref="TypeConverter.StandardValuesCollection"/> that holds a standard set of valid values,
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/// or null if the data type does not support a standard set of values.
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/// </returns>
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public override StandardValuesCollection GetStandardValues(ITypeDescriptorContext context)
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{
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return _valuesFactory != null
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? new StandardValuesCollection(_valuesFactory.Invoke())
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: EmptyStandardValuesCollection;
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}
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}
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