C# TypeConverter.ConvertFrom方法代碼示例

 private object GetValue(DateTime dateTime, Type type, TypeConverter converter)
 {
     if (type.IsAssignableFrom(typeof(DateTime)))
         return dateTime;
     else
         return converter.ConvertFrom(dateTime);
 }

		private void SetValueFromConverter(string newValue, Type targetType, TypeConverter converter)
		{
			if (!converter.CanConvertFrom(targetType) && string.IsNullOrEmpty(newValue))
			{
				this.Value = null;
			}
			else
			{
				this.Value = converter.ConvertFrom(newValue);
			}
		}

		public virtual object ParseFormattedValue (object formattedValue, DataGridViewCellStyle cellStyle, TypeConverter formattedValueTypeConverter, TypeConverter valueTypeConverter)
		{
			if (cellStyle == null)
				throw new ArgumentNullException ("cellStyle is null.");
			if (FormattedValueType == null)
				throw new FormatException ("The System.Windows.Forms.DataGridViewCell.FormattedValueType property value is null.");
			if (formattedValue == null)
				throw new ArgumentException ("formattedValue is null.");
			if (ValueType == null)
				throw new FormatException ("valuetype is null");
			if (!FormattedValueType.IsAssignableFrom (formattedValue.GetType ()))
				throw new ArgumentException ("formattedValue is not of formattedValueType.");
			
			if (formattedValueTypeConverter == null)
				formattedValueTypeConverter = FormattedValueTypeConverter;
			if (valueTypeConverter == null)
				valueTypeConverter = ValueTypeConverter;

			if (valueTypeConverter != null && valueTypeConverter.CanConvertFrom (FormattedValueType))
				return valueTypeConverter.ConvertFrom (formattedValue);
			if (formattedValueTypeConverter != null && formattedValueTypeConverter.CanConvertTo (ValueType))
				return formattedValueTypeConverter.ConvertTo (formattedValue, ValueType);
			return Convert.ChangeType (formattedValue, ValueType);
		}

        /// <devdoc>
        ///
        /// Converts a value into a format suitable for display to the end user.
        ///
        /// - Converts DBNull or null into a suitable formatted representation of 'null'
        /// - Performs some special-case conversions (eg. Boolean to CheckState)
        /// - Uses TypeConverters or IConvertible where appropriate
        /// - Throws a FormatException is no suitable conversion can be found
        ///
        /// </devdoc>
        private static object FormatObjectInternal(object value,
                                                   Type targetType, 
                                                   TypeConverter sourceConverter, 
                                                   TypeConverter targetConverter, 
                                                   string formatString, 
                                                   IFormatProvider formatInfo, 
                                                   object formattedNullValue) {
            if (value == System.DBNull.Value || value == null) {
                //
                // Convert DBNull to the formatted representation of 'null' (if possible)
                //
                if (formattedNullValue != null)
                {
                    return formattedNullValue;
                }

                //
                // Convert DBNull or null to a specific 'known' representation of null (otherwise fail)
                //
                if (targetType == stringType)
                {
                    return String.Empty;
                }
                
                if (targetType == checkStateType) {
                    return CheckState.Indeterminate;
                }
                
                // Just pass null through: if this is a value type, it's been unwrapped here, so we return null 
                // and the caller has to wrap if appropriate.
                return null; 
            }

            //
            // Special case conversions
            //

            if (targetType == stringType) {
                if (value is IFormattable && !String.IsNullOrEmpty(formatString)) {
                    return (value as IFormattable).ToString(formatString, formatInfo);
                }
            }

            //The converters for properties should take precedence.  Unfortunately, we don't know whether we have one.  Check vs. the 
            //type's TypeConverter.  We're punting the case where the property-provided converter is the same as the type's converter.
            Type sourceType = value.GetType();
            TypeConverter sourceTypeTypeConverter = TypeDescriptor.GetConverter(sourceType);
            if (sourceConverter != null && sourceConverter != sourceTypeTypeConverter && sourceConverter.CanConvertTo(targetType)) {
                return sourceConverter.ConvertTo(null, GetFormatterCulture(formatInfo), value, targetType);
            }

            TypeConverter targetTypeTypeConverter = TypeDescriptor.GetConverter(targetType);
            if (targetConverter != null && targetConverter != targetTypeTypeConverter && targetConverter.CanConvertFrom(sourceType)) {
                return targetConverter.ConvertFrom(null, GetFormatterCulture(formatInfo), value);
            }

            if (targetType == checkStateType) {
                if (sourceType == booleanType) {
                    return ((bool)value) ? CheckState.Checked : CheckState.Unchecked;
                } 
                else {
                    if (sourceConverter == null) {
                        sourceConverter = sourceTypeTypeConverter;
                    }
                    if (sourceConverter != null && sourceConverter.CanConvertTo(booleanType)) {
                        return (bool)sourceConverter.ConvertTo(null, GetFormatterCulture(formatInfo), value, booleanType)
                            ? CheckState.Checked : CheckState.Unchecked;
                    }
                }
            }

            if (targetType.IsAssignableFrom(sourceType)) {
                return value;
            }

            //
            // If explicit type converters not provided, supply default ones instead
            //

            if (sourceConverter == null) {
                sourceConverter = sourceTypeTypeConverter;
            }

            if (targetConverter == null) {
                targetConverter = targetTypeTypeConverter;
            }

            //
            // Standardized conversions
            //
//.........這裏部分代碼省略.........

        /// <devdoc>
        ///
        /// Converts a value entered by the end user (through UI) into the corresponding binary value.
        ///
        /// - Converts formatted representations of 'null' into DBNull
        /// - Performs some special-case conversions (eg. CheckState to Boolean)
        /// - Uses TypeConverters or IConvertible where appropriate
        /// - Throws a FormatException is no suitable conversion can be found
        ///
        /// </devdoc>
        private static object ParseObjectInternal(object value, 
                                                  Type targetType, 
                                                  Type sourceType, 
                                                  TypeConverter targetConverter, 
                                                  TypeConverter sourceConverter, 
                                                  IFormatProvider formatInfo, 
                                                  object formattedNullValue) {
            //
            // Convert the formatted representation of 'null' to DBNull (if possible)
            //

            if (EqualsFormattedNullValue(value, formattedNullValue, formatInfo) || value == System.DBNull.Value) {
                return System.DBNull.Value;
            }

            //
            // Special case conversions
            //

            TypeConverter targetTypeTypeConverter = TypeDescriptor.GetConverter(targetType);
            if (targetConverter != null && targetTypeTypeConverter != targetConverter && targetConverter.CanConvertFrom(sourceType)) {
                return targetConverter.ConvertFrom(null, GetFormatterCulture(formatInfo), value);
            }

            TypeConverter sourceTypeTypeConverter = TypeDescriptor.GetConverter(sourceType);
            if (sourceConverter != null && sourceTypeTypeConverter != sourceConverter && sourceConverter.CanConvertTo(targetType)) {
                return sourceConverter.ConvertTo(null, GetFormatterCulture(formatInfo), value, targetType);
            }

            if (value is string) {
                // If target type has a suitable Parse method, use that to parse strings
                object parseResult = InvokeStringParseMethod(value, targetType, formatInfo);
                if (parseResult != parseMethodNotFound) {
                    return parseResult;
                }
            }
            else if (value is CheckState) {
                CheckState state = (CheckState)value;
                if (state == CheckState.Indeterminate) {
                    return DBNull.Value;
                }
                // Explicit conversion from CheckState to Boolean
                if (targetType == booleanType) {
                    return (state == CheckState.Checked);
                }
                if (targetConverter == null) {
                    targetConverter = targetTypeTypeConverter;
                }
                if (targetConverter != null && targetConverter.CanConvertFrom(booleanType)) {
                    return targetConverter.ConvertFrom(null, GetFormatterCulture(formatInfo), state == CheckState.Checked);
                }
            }
            else if (value != null && targetType.IsAssignableFrom(value.GetType())) {
                // If value is already of a compatible type, just go ahead and use it
                return value;
            }

            //
            // If explicit type converters not provided, supply default ones instead
            //

            if (targetConverter == null) {
                targetConverter = targetTypeTypeConverter;
            }

            if (sourceConverter == null) {
                sourceConverter = sourceTypeTypeConverter;
            }

            //
            // Standardized conversions
            //

            if (targetConverter != null && targetConverter.CanConvertFrom(sourceType)) {
                return targetConverter.ConvertFrom(null, GetFormatterCulture(formatInfo), value);
            }
            else if (sourceConverter != null && sourceConverter.CanConvertTo(targetType)) {
                return sourceConverter.ConvertTo(null, GetFormatterCulture(formatInfo), value, targetType);
            }
            else if (value is IConvertible) {
                return ChangeType(value, targetType, formatInfo);
            }

            //
            // Fail if no suitable conversion found
            //

            throw new FormatException(GetCantConvertMessage(value, targetType));
        }

		/// Generic function to read an object value.  Returns true if the read
		/// succeeded.
		private bool ReadValue(XmlNode node, TypeConverter converter, ArrayList errors, out object value)
		{
			try
			{
				foreach (XmlNode child in node.ChildNodes)
				{
					if (child.NodeType == XmlNodeType.Text)
					{
						value = converter.ConvertFromInvariantString(node.InnerText);
						return true;
					}
					else if (child.Name.Equals("Binary"))
					{
						byte[] data = Convert.FromBase64String(child.InnerText);

						// Binary blob.  Now, check to see if the type converter
						// can convert it.  If not, use serialization.
						//
						if (GetConversionSupported(converter, typeof(byte[])))
						{
							value = converter.ConvertFrom(null, CultureInfo.InvariantCulture, data);
							return true;
						}
						else
						{
							BinaryFormatter formatter = new BinaryFormatter();
							MemoryStream stream = new MemoryStream(data);

							value = formatter.Deserialize(stream);
							return true;
						}
					}
					else if (child.Name.Equals("InstanceDescriptor"))
					{
						value = ReadInstanceDescriptor(child, errors);
						return (value != null);
					}
					else
					{
						errors.Add(string.Format("Unexpected element type {0}", child.Name));
						value = null;
						return false;
					}
				}

				// If we get here, it is because there were no nodes.  No nodes and no inner
				// text is how we signify null.
				//
				value = null;
				return true;
			}
			catch (Exception ex)
			{
				errors.Add(ex.Message);
				value = null;
				return false;
			}
		}

		object ConvertData (TypeConverter c)
		{
			if (mime_type == ResXResourceWriter.ByteArraySerializedObjectMimeType) {
				if (c.CanConvertFrom (typeof (byte [])))
					return c.ConvertFrom (Convert.FromBase64String (dataString));
			} else if (String.IsNullOrEmpty (mime_type)) {
				if (c.CanConvertFrom (typeof (string)))
					return c.ConvertFromInvariantString (dataString);
			}
			else
				throw new Exception ("shouldnt get here, invalid mime type");

			throw new TypeLoadException ("No converter for this type found");
		}

		/// <summary>
		/// Creates a new instance of the ConfigurationProperty class.
		/// </summary>
		/// <param name="name">The name of the xml entity.</param>
		/// <param name="type">The type of the xml entity.</param>
		/// <param name="defaultValue">The default value of the xml entity.</param>
		/// <param name="converter">The type of the converter to apply.</param>
		/// <param name="validation">The validator to use.</param>
		/// <param name="flags">One of the APXmlPropertyOptions enumeration values.</param>
		/// <param name="description">The description of the xml entity.</param>
		public APXmlProperty(string name, Type type, object defaultValue,
			TypeConverter converter, APValidatorBase validation, APXmlPropertyOptions flags, string description)
		{
			_name = name;

			_converter = converter != null ? converter : TypeDescriptor.GetConverter(type);

			if (defaultValue != null)
			{
				if (defaultValue == NoDefaultValue)
				{
					switch (Type.GetTypeCode(type))
					{
						case TypeCode.Object:
							defaultValue = null;
							break;
						case TypeCode.String:
							defaultValue = String.Empty;
							break;
						default:
							defaultValue = Activator.CreateInstance(type);
							break;
					}
				}
				else
				{
					if (!type.IsAssignableFrom(defaultValue.GetType()))
					{
						if (!_converter.CanConvertFrom(defaultValue.GetType()))
							throw new APXmlException(APResource.GetString(APResource.APXml_DefaultValueTypeError, name, type, defaultValue.GetType()));
						defaultValue = _converter.ConvertFrom(defaultValue);
					}
				}
			}

			_defaultValue = defaultValue;
			_flags = flags;
			_type = type;
			_validation = validation != null ? validation : new DefaultAPValidator();
			_description = description;
		}

			protected override object Read (byte token, BinaryReader r, ReaderContext ctx)
			{
				Type t = (Type) ObjectFormatter.ReadObject (r, ctx);
				converter = TypeDescriptor.GetConverter (t);
				token = r.ReadByte ();
				string v = (string) base.Read (token, r, ctx);
				return converter.ConvertFrom (null, Helpers.InvariantCulture, v);
			}

        /// <summary>
        /// ��ȡ"Value"�ڵ�
        /// �������ԣ��������ĵ��е�����ֵ�������͵�ת����ת��Ϊ��ǰ���Ե�ֵ����
        /// </summary>
        /// <param name="node">���ڵ�</param>
        /// <param name="converter">���͵�ת����</param>
        /// <param name="errors">�����ڼ������Ĵ�������еĻ����ļ���</param>
        /// <param name="value">����</param>
        /// <returns>��ֵ�Ƿ��ܹ���ת������Ҫ������</returns>
        private bool ReadValue(XmlNode node, TypeConverter converter, ArrayList errors, ref object value)
        {
            try
            {
                foreach (XmlNode child in node.ChildNodes)
                {
                    //XmlNodeTypeö��ָ���ڵ�����͡�.Text:�ڵ���ı����ݡ�Text �ڵ㲻�ܾ����κ��ӽڵ㡣
                    if (child.NodeType == XmlNodeType.Text)
                    {
                        value = converter.ConvertFromInvariantString(node.InnerText);
                        return true;
                    }
                    else if (child.Name.Equals("Binary"))
                    {
                        byte[] data = Convert.FromBase64String(child.InnerText);

                        if (GetConversionSupported(converter, typeof(byte[])))
                        {
                            value = converter.ConvertFrom(data);
                            return true;
                        }
                        else
                        {
                            BinaryFormatter formatter = new BinaryFormatter();
                            MemoryStream stream = new MemoryStream(data);

                            value = formatter.Deserialize(stream);
                            return true;
                        }
                    }

                    else
                    {
                        errors.Add(string.Format("��������{0}", child.Name));
                        value = null;
                        return false;
                    }
                }
                return true;
            }
            catch (Exception ex)
            {
                errors.Add(ex.Message);
                value = null;
                return false;
            }
        }

		public void CheckConversion(object check, object expect, TypeConverter conv, Type type, bool test_from, bool test_to, CultureInfo culture) {
			object obj;
			object result;

			obj = check;

			if (debug > 0) {
				Console.WriteLine("{0}: CheckConversion, checking {1}({2}) <-> {3}({4})", conv.ToString(), check.GetType().ToString(), check.ToString(), type.ToString(), expect != null ? expect.ToString() : "null");
			}

			if (test_to) {
				obj = conv.ConvertTo(null, culture, check, type);

				if (obj == null) {
					if (expect != null) {
						failed++;
						Console.WriteLine("{0}: ConvertTo failed, type {1}, expected {2}, got null", conv.ToString(), type.ToString(), expect.ToString());
					}
					return;
				}

				// Intermediate verification
				if (expect != null && !obj.Equals(expect)) {
					failed++;
					if (verbose > 0) {
						Console.WriteLine("{0}: ConvertTo failed, type {1}, expected {2}, got {3}", conv.ToString(), type.ToString(), expect.ToString(), obj.ToString());
					}
				}

				if (debug > 1) {
					Console.WriteLine("{0}: CheckConversion, ConvertTo result: '{1}')", conv.ToString(), obj);
				}
			}


			if (test_from) {
				result = conv.ConvertFrom(null, culture, obj);

				if (test_to) {
					// Roundtrip check
					if (!check.Equals(result)) {
						failed++;
						if (verbose > 0) {
							Console.WriteLine("{0}: ConvertTo/ConvertFrom roundtrip failed, type {1}", conv.ToString(), type.ToString());
						}
					}

				} else {
					if (!expect.Equals(result)) {
						failed++;
						if (verbose > 0) {
							Console.WriteLine("{0}: ConvertFrom failed, type {1}", conv.ToString(), type.ToString());
						}
					}
				}

				if (debug > 1) {
					Console.WriteLine("{0}: CheckConversion, ConvertFrom result: '{1}')", conv.ToString(), result);
				}
			}
		}

      private static bool TryConvertTo( object value, Type targetType, CultureInfo culture, TypeConverter converter, out object result )
      {
        if( converter != null )
        {
          try
          {
            result = converter.ConvertTo( null, culture, value, targetType );
            return true;
          }
          catch
          {
            // We'll try to convert the value another way.
          }

          if( ( value != null ) && ( converter.CanConvertFrom( value.GetType() ) ) )
          {
            try
            {
              var newValue = converter.ConvertFrom( null, culture, value );
              result = converter.ConvertTo( null, culture, newValue, targetType );

              return true;
            }
            catch
            {
            }
          }
        }

        result = null;
        return false;
      }

        /// <summary>
        /// ��ȡ"Value"�ڵ�
        /// �������ԣ��������ĵ��е�����ֵ�������͵�ת����ת��Ϊ��ǰ���Ե�ֵ����
        /// </summary>
        /// <param name="node">���ڵ�</param>
        /// <param name="converter">���͵�ת����</param>  
        /// <param name="value">����</param>
        /// <returns>��ֵ�Ƿ��ܹ���ת������Ҫ������</returns>
        private bool ReadValue(XmlNode node, TypeConverter converter, ref object value)
        {
            try
            {
                foreach (XmlNode child in node.ChildNodes)
                {
                    //XmlNodeTypeö��ָ���ڵ�����͡�.Text:�ڵ���ı����ݡ�Text �ڵ㲻�ܾ����κ��ӽڵ㡣
                    if (child.NodeType == XmlNodeType.Text)
                    {
                        value = converter.ConvertFromInvariantString(node.InnerText);
                        return true;
                    }
                    else if (child.NodeType == XmlNodeType.Element)
                    {//������Ϣ�ڵ����ô˲��ֶ�ȡ����ӿ���Ϣ20090616
                        List<string> tempIO = new List<string>();
                        for (int i = 0; i < node.ChildNodes.Count; i++)
                        {
                            tempIO.Add(node.ChildNodes[i].Attributes["name"].Value);
                        }
                        value = String.Join(",", tempIO.ToArray());
                        return true;
                    }
                    else if (child.Name.Equals("Binary"))
                    {
                        byte[] data = Convert.FromBase64String(child.InnerText);

                        if (GetConversionSupported(converter, typeof(byte[])))
                        {
                            value = converter.ConvertFrom(data);
                            return true;
                        }
                        else
                        {
                            BinaryFormatter formatter = new BinaryFormatter();
                            MemoryStream stream = new MemoryStream(data);

                            value = formatter.Deserialize(stream);
                            return true;
                        }
                    }

                    else
                    {
                        value = null;
                        return false;
                    }
                }
                return true;
            }
            catch (Exception ex)
            {
                value = null;
                return false;
            }
        }

 private static bool ConvertObjectToTypeInternal(object o, Type type, JavaScriptSerializer serializer, bool throwOnError, out object convertedObject)
 {
     IDictionary<string, object> dictionary = o as IDictionary<string, object>;
     if (dictionary != null)
     {
         return ConvertDictionaryToObject(dictionary, type, serializer, throwOnError, out convertedObject);
     }
     IList list = o as IList;
     if (list != null)
     {
         IList list2;
         if (ConvertListToObject(list, type, serializer, throwOnError, out list2))
         {
             convertedObject = list2;
             return true;
         }
         convertedObject = null;
         return false;
     }
     if ((type == null) || (o.GetType() == type))
     {
         convertedObject = o;
         return true;
     }
     //TypeDescriptor.GetConverter(type) !!!
     TypeConverter converter = new TypeConverter();
     if (converter.CanConvertFrom(o.GetType()))
     {
         try
         {
             convertedObject = converter.ConvertFrom(null, CultureInfo.InvariantCulture, o);
             return true;
         }
         catch
         {
             if (throwOnError)
             {
                 throw;
             }
             convertedObject = null;
             return false;
         }
     }
     if (converter.CanConvertFrom(typeof(string)))
     {
         try
         {
             string str;
             if (o is DateTime)
             {
                 DateTime time = (DateTime)o;
                 str = time.ToUniversalTime().ToString("u", CultureInfo.InvariantCulture);
             }
             else
             {
                 //ConvertToInvariantString(o); !!!
                 str = converter.ConvertToString(o);
             }
             //ConvertFromInvariantString(str); !!!
             convertedObject = converter.ConvertToString(str);
             return true;
         }
         catch
         {
             if (throwOnError)
             {
                 throw;
             }
             convertedObject = null;
             return false;
         }
     }
     if (type.IsAssignableFrom(o.GetType()))
     {
         convertedObject = o;
         return true;
     }
     if (throwOnError)
     {
         throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, AtlasWeb.JSON_CannotConvertObjectToType, new object[] { o.GetType(), type }));
     }
     convertedObject = null;
     return false;
 }

		protected virtual object GetFormattedValue (object value, int rowIndex, ref DataGridViewCellStyle cellStyle, TypeConverter valueTypeConverter, TypeConverter formattedValueTypeConverter, DataGridViewDataErrorContexts context)
		{
			if (DataGridView == null)
				return null;
				
			if (rowIndex < 0 || rowIndex >= DataGridView.RowCount)
				throw new ArgumentOutOfRangeException ("rowIndex");

			// Give the user a chance to custom format
			if (!(this is DataGridViewRowHeaderCell)) {
				DataGridViewCellFormattingEventArgs e = new DataGridViewCellFormattingEventArgs (ColumnIndex, rowIndex, value, FormattedValueType, cellStyle);
				DataGridView.OnCellFormattingInternal (e);
			
				if (e.FormattingApplied)
					return e.Value;
			
				cellStyle = e.CellStyle;
				value = e.Value;
			}
			
			if (value == null || (cellStyle != null && value == cellStyle.DataSourceNullValue)) {
				if (FormattedValueType == typeof (string))
					return String.Empty;
			}

			if (FormattedValueType == typeof(string) && value is IFormattable && !String.IsNullOrEmpty (cellStyle.Format))
				return ((IFormattable) value).ToString (cellStyle.Format, cellStyle.FormatProvider);
			if (value != null && FormattedValueType.IsAssignableFrom (value.GetType()))
				return value;

			if (formattedValueTypeConverter == null)
				formattedValueTypeConverter = FormattedValueTypeConverter;
			if (valueTypeConverter == null)
				valueTypeConverter = ValueTypeConverter;

			if (valueTypeConverter != null && valueTypeConverter.CanConvertTo (FormattedValueType))
				return valueTypeConverter.ConvertTo (value, FormattedValueType);
			if (formattedValueTypeConverter != null && formattedValueTypeConverter.CanConvertFrom (ValueType))
				return formattedValueTypeConverter.ConvertFrom (value);

			return Convert.ChangeType (value, FormattedValueType);
		}