自定义SettingsProvider并检索默认值

发布于 2024-10-17 18:12:29 字数 811 浏览 2 评论 0原文

我已经实现了自己的类，该类继承自 SettingsProvider 类。如果我检索的值尚未由用户设置，即这是程序第一次启动，我会尝试获取默认值。我看到的问题是，当从 SettingsProperty 检索默认值时，它会以字符串形式返回。我尝试添加一些转换项目的代码，但在转换 System.Drawing.Colors 时遇到问题，并收到错误“从‘System.String’到‘System.Drawing.Color’的转换无效。”。

这是我用来获取默认值的代码示例：

 private object GetDefaultValue(SettingsProperty setting)
  {
         if (setting.PropertyType.IsEnum)
             return Enum.Parse(setting.PropertyType, setting.DefaultValue.ToString());

        // Return the default value if it is set
        if (setting.DefaultValue != null)
           return Convert.ChangeType(setting.DefaultValue, setting.PropertyType);
        else // If there is no default value return the default object
           return Activator.CreateInstance(setting.PropertyType);
   }

如何正确地将默认值转换为正确的类型？

原文

I have implemented my own class that inherits from the SettingsProvider class. If the value I am retrieving has not been set by the user, i.e. it is the first time the program starts, I attempt to grab the default value. The problem I am seeing is when the default value is retrieved from the SettingsProperty it comes back as a string. I have tried to add some code that converts the item but I am running into problems when converting System.Drawing.Colors and am receiving the error "Invalid cast from 'System.String' to 'System.Drawing.Color'.".

Here is an example of the code I am using to get the default value:

 private object GetDefaultValue(SettingsProperty setting)
  {
         if (setting.PropertyType.IsEnum)
             return Enum.Parse(setting.PropertyType, setting.DefaultValue.ToString());

        // Return the default value if it is set
        if (setting.DefaultValue != null)
           return Convert.ChangeType(setting.DefaultValue, setting.PropertyType);
        else // If there is no default value return the default object
           return Activator.CreateInstance(setting.PropertyType);
   }

How can I properly convert the default value to the correct type?

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只有影子陪我不离不弃 2024-10-24 18:12:29

好的。所以我找到了答案。您需要根据 settings.PropertyType 实际上创建一个 TypeConverter 实例，而不是使用 Convert.ChangeType。这段代码的工作原理：

private object GetDefaultValue(SettingsProperty setting)
  {
         if (setting.PropertyType.IsEnum)
             return Enum.Parse(setting.PropertyType, setting.DefaultValue.ToString());

        // Return the default value if it is set
        // Return the default value if it is set
         if (setting.DefaultValue != null)
         {
             System.ComponentModel.TypeConverter tc = System.ComponentModel.TypeDescriptor.GetConverter(setting.PropertyType);
             return tc.ConvertFromString(setting.DefaultValue.ToString());
         }
         else // If there is no default value return the default object
         {
             return Activator.CreateInstance(setting.PropertyType);
         }
   }

Ok. So I found the answer. Instead of using Convert.ChangeType you need to actually create a TypeConverter instance against the settings.PropertyType. This code Works:

private object GetDefaultValue(SettingsProperty setting)
  {
         if (setting.PropertyType.IsEnum)
             return Enum.Parse(setting.PropertyType, setting.DefaultValue.ToString());

        // Return the default value if it is set
        // Return the default value if it is set
         if (setting.DefaultValue != null)
         {
             System.ComponentModel.TypeConverter tc = System.ComponentModel.TypeDescriptor.GetConverter(setting.PropertyType);
             return tc.ConvertFromString(setting.DefaultValue.ToString());
         }
         else // If there is no default value return the default object
         {
             return Activator.CreateInstance(setting.PropertyType);
         }
   }

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