lengthconverter.cs source code in C# .NET

                        Code:
                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Framework / System / Windows / lengthconverter.cs / 1 / lengthconverter.cs
                        
                        
                            //---------------------------------------------------------------------------- 
//
// Copyright (C) Microsoft Corporation.  All rights reserved.
//
// File: LengthConverter.cs 
//
// Description: Contains the LengthConverter: TypeConverter for the Length class. 
// 
// History:
//  06/27/2003 : wwilaria  - Initial implementation 
//
//---------------------------------------------------------------------------

using System; 
using System.ComponentModel;
 
using System.ComponentModel.Design.Serialization; 
using System.Diagnostics;
using System.Globalization; 
using System.Reflection;
using System.Windows;
using System.Windows.Markup;
using System.Security; 
using MS.Internal;
using MS.Utility; 
 
namespace System.Windows
{ 

    /// 
    /// LengthConverter - Converter class for converting instances of other types to and from double representing length.
    ///  
    public class LengthConverter: TypeConverter
    { 
        //------------------------------------------------------------------- 
        //
        //  Public Methods 
        //
        //-------------------------------------------------------------------

        #region Public Methods 

        ///  
        /// CanConvertFrom - Returns whether or not this class can convert from a given type. 
        /// 
        ///  
        /// bool - True if thie converter can convert from the provided type, false if not.
        /// 
        ///  The ITypeDescriptorContext for this call. 
        ///  The Type being queried for support.  
        public override bool CanConvertFrom(ITypeDescriptorContext typeDescriptorContext, Type sourceType)
        { 
            // We can only handle strings, integral and floating types 
            TypeCode tc = Type.GetTypeCode(sourceType);
            switch (tc) 
            {
                case TypeCode.String:
                case TypeCode.Decimal:
                case TypeCode.Single: 
                case TypeCode.Double:
                case TypeCode.Int16: 
                case TypeCode.Int32: 
                case TypeCode.Int64:
                case TypeCode.UInt16: 
                case TypeCode.UInt32:
                case TypeCode.UInt64:
                    return true;
                default: 
                    return false;
            } 
        } 

        ///  
        /// CanConvertTo - Returns whether or not this class can convert to a given type.
        /// 
        /// 
        /// bool - True if this converter can convert to the provided type, false if not. 
        /// 
        ///  The ITypeDescriptorContext for this call.  
        ///  The Type being queried for support.  
        public override bool CanConvertTo(ITypeDescriptorContext typeDescriptorContext, Type destinationType)
        { 
            // We can convert to an InstanceDescriptor or to a string.
            if (destinationType == typeof(InstanceDescriptor) ||
                destinationType == typeof(string))
            { 
                return true;
            } 
            else 
            {
                return false; 
            }
        }

        ///  
        /// ConvertFrom - Attempt to convert to a length from the given object
        ///  
        ///  
        /// The double representing the size in 1/96th of an inch.
        ///  
        /// 
        /// An ArgumentNullException is thrown if the example object is null.
        /// 
        ///  
        /// An ArgumentException is thrown if the example object is not null and is not a valid type
        /// which can be converted to a double. 
        ///  
        ///  The ITypeDescriptorContext for this call. 
        ///  The CultureInfo which is respected when converting.  
        ///  The object to convert to a double. 
        public override object ConvertFrom(ITypeDescriptorContext typeDescriptorContext,
                                           CultureInfo cultureInfo,
                                           object source) 
        {
            if (source != null) 
            { 
                if (source is string) { return FromString((string)source, cultureInfo); }
                else                  { return (double)(Convert.ToDouble(source, cultureInfo)); } 
            }

            throw GetConvertFromException(source);
        } 

        ///  
        /// ConvertTo - Attempt to convert a double to the given type 
        /// 
        ///  
        /// The object which was constructed.
        /// 
        /// 
        /// An ArgumentNullException is thrown if the example object is null. 
        /// 
        ///  
        /// An ArgumentException is thrown if the object is not null, 
        /// or if the destinationType isn't one of the valid destination types.
        ///  
        ///  The ITypeDescriptorContext for this call. 
        ///  The CultureInfo which is respected when converting. 
        ///  The double to convert. 
        /// The type to which to convert the double.  
        ///
        ///     Critical: calls InstanceDescriptor ctor which LinkDemands 
        ///     PublicOK: can only make an InstanceDescriptor for double, not an arbitrary class 
        ///
        [SecurityCritical] 
        public override object ConvertTo(ITypeDescriptorContext typeDescriptorContext,
                                         CultureInfo cultureInfo,
                                         object value,
                                         Type destinationType) 
        {
            if (destinationType == null) 
            { 
                throw new ArgumentNullException("destinationType");
            } 

            if (    value != null
                &&  value is double )
            { 
                double l = (double)value;
                if (destinationType == typeof(string)) 
                { 
                    if(DoubleUtil.IsNaN(l))
                        return "Auto"; 
                    else
                        return Convert.ToString(l, cultureInfo);
                }
                else if (destinationType == typeof(InstanceDescriptor)) 
                {
                    ConstructorInfo ci = typeof(double).GetConstructor(new Type[] { typeof(double) }); 
                    return new InstanceDescriptor(ci, new object[] { l }); 
                }
            } 
            throw GetConvertToException(value, destinationType);
        }
        #endregion
 
        //--------------------------------------------------------------------
        // 
        //  Internal Methods 
        //
        //------------------------------------------------------------------- 

        #region Internal Methods

 
        // Parse a Length from a string given the CultureInfo.
        // Formats: 
        //"[value][unit]" 
        //   [value] is a double
        //   [unit] is a string specifying the unit, like 'in' or 'px', or nothing (means pixels) 
        // NOTE - This code is called from FontSizeConverter, so changes will affect both.
        static internal double FromString(string s, CultureInfo cultureInfo)
        {
            string valueString = s.Trim(); 
            string goodString = valueString.ToLowerInvariant();
            int strLen = goodString.Length; 
            int strLenUnit = 0; 
            double unitFactor = 1.0;
 
            //Auto is represented and Double.NaN
            //properties that do not want Auto and NaN to be in their ligit values,
            //should disallow NaN in validation callbacks (same goes for negative values)
            if (goodString == "auto") return Double.NaN; 

            for (int i = 0; i < PixelUnitStrings.Length; i++) 
            { 
                // NOTE: This is NOT a culture specific comparison.
                // This is by design: we want the same unit string table to work across all cultures. 
                if (goodString.EndsWith(PixelUnitStrings[i], StringComparison.Ordinal))
                {
                    strLenUnit = PixelUnitStrings[i].Length;
                    unitFactor = PixelUnitFactors[i]; 
                    break;
                } 
            } 

            //  important to substring original non-lowered string 
            //  this allows case sensitive ToDouble below handle "NaN" and "Infinity" correctly.
            //  this addresses windows bug 1177408
            valueString = valueString.Substring(0, strLen - strLenUnit);
 
            // FormatException errors thrown by Convert.ToDouble are pretty uninformative.
            // Throw a more meaningful error in this case that tells that we were attempting 
            // to create a Length instance from a string.  This addresses windows bug 968884 
            try
            { 
                double result = Convert.ToDouble(valueString, cultureInfo) * unitFactor;
                return result;
            }
            catch (FormatException) 
            {
                throw new FormatException(SR.Get(SRID.LengthFormatError, valueString)); 
            } 
        }
 
        // This array contains strings for unit types
        // These are effectively "TypeConverter only" units.
        // They are all expressable in terms of the Pixel unit type and a conversion factor.
        static private string[] PixelUnitStrings = { "px", "in", "cm", "pt" }; 
        static private double[] PixelUnitFactors =
        { 
            1.0,              // Pixel itself 
            96.0,             // Pixels per Inch
            96.0 / 2.54,      // Pixels per Centimeter 
            96.0 / 72.0,      // Pixels per Point
        };

        static internal string ToString(double l, CultureInfo cultureInfo) 
        {
            if(DoubleUtil.IsNaN(l)) return "Auto"; 
            return Convert.ToString(l, cultureInfo); 
        }
 
        #endregion

    }
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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