功能“递归模式”在 C# 7.3 中不可用，请使用 8.0 或更高的语言版本的一种兼容处理方案
原程序：
internal class ControllerParameterCreator : IParameterCreator
{private Controller controller;public ControllerParameterCreator(Controller controller){this.controller = controller;}public Parameter CreateSystem(string name, int unused){return ParameterInfoProvider.GetType(name) switch{PrimitiveType.Double => new ControllerParameter<double>(controller, name, PrimitiveType.Double),PrimitiveType.Integer => new ControllerParameter<int>(controller, name, PrimitiveType.Integer),PrimitiveType.Long => new ControllerParameter<long>(controller, name, PrimitiveType.Long),PrimitiveType.Single => new ControllerParameter<float>(controller, name, PrimitiveType.Single),PrimitiveType.String => new ControllerParameter<string>(controller, name, PrimitiveType.String),_ => null,};}public Parameter CreateAxis(string name, int index){return ParameterInfoProvider.GetType(name) switch{PrimitiveType.Double => new ControllerParameter<double>(controller, name, PrimitiveType.Double, ParameterContext.Axis, index),PrimitiveType.Integer => new ControllerParameter<int>(controller, name, PrimitiveType.Integer, ParameterContext.Axis, index),PrimitiveType.Long => new ControllerParameter<long>(controller, name, PrimitiveType.Long, ParameterContext.Axis, index),PrimitiveType.Single => new ControllerParameter<float>(controller, name, PrimitiveType.Single, ParameterContext.Axis, index),PrimitiveType.String => new ControllerParameter<string>(controller, name, PrimitiveType.String, ParameterContext.Axis, index),_ => null,};}public Parameter CreateTask(string name, int task){return ParameterInfoProvider.GetType(name) switch{PrimitiveType.Double => new ControllerParameter<double>(controller, name, PrimitiveType.Double, ParameterContext.Task, task),PrimitiveType.Integer => new ControllerParameter<int>(controller, name, PrimitiveType.Integer, ParameterContext.Task, task),PrimitiveType.Long => new ControllerParameter<long>(controller, name, PrimitiveType.Long, ParameterContext.Task, task),PrimitiveType.Single => new ControllerParameter<float>(controller, name, PrimitiveType.Single, ParameterContext.Task, task),PrimitiveType.String => new ControllerParameter<string>(controller, name, PrimitiveType.String, ParameterContext.Task, task),_ => null,};}
}处理后程序：
internal class ControllerParameterCreator : IParameterCreator
{private Controller controller;public ControllerParameterCreator(Controller controller){this.controller = controller;}public Parameter CreateSystem(string name, int unused){
#if CSHARP_8_OR_NEWER// C# 8.0+ 递归模式写法return ParameterInfoProvider.GetType(name) switch{PrimitiveType.Double => new ControllerParameter<double>(controller, name, PrimitiveType.Double),PrimitiveType.Integer => new ControllerParameter<int>(controller, name, PrimitiveType.Integer),PrimitiveType.Long => new ControllerParameter<long>(controller, name, PrimitiveType.Long),PrimitiveType.Single => new ControllerParameter<float>(controller, name, PrimitiveType.Single),PrimitiveType.String => new ControllerParameter<string>(controller, name, PrimitiveType.String),_ => null,};
#else// C# 7.3 传统 switch 写法PrimitiveType type = ParameterInfoProvider.GetType(name);switch (type){case PrimitiveType.Double:return new ControllerParameter<double>(controller, name, PrimitiveType.Double);case PrimitiveType.Integer:return new ControllerParameter<int>(controller, name, PrimitiveType.Integer);case PrimitiveType.Long:return new ControllerParameter<long>(controller, name, PrimitiveType.Long);case PrimitiveType.Single:return new ControllerParameter<float>(controller, name, PrimitiveType.Single);case PrimitiveType.String:return new ControllerParameter<string>(controller, name, PrimitiveType.String);default:return null;}
#endif}public Parameter CreateAxis(string name, int index){
#if CSHARP_8_OR_NEWERreturn ParameterInfoProvider.GetType(name) switch{PrimitiveType.Double => new ControllerParameter<double>(controller, name, PrimitiveType.Double, ParameterContext.Axis, index),PrimitiveType.Integer => new ControllerParameter<int>(controller, name, PrimitiveType.Integer, ParameterContext.Axis, index),PrimitiveType.Long => new ControllerParameter<long>(controller, name, PrimitiveType.Long, ParameterContext.Axis, index),PrimitiveType.Single => new ControllerParameter<float>(controller, name, PrimitiveType.Single, ParameterContext.Axis, index),PrimitiveType.String => new ControllerParameter<string>(controller, name, PrimitiveType.String, ParameterContext.Axis, index),_ => null,};
#elsePrimitiveType type = ParameterInfoProvider.GetType(name);switch (type){case PrimitiveType.Double:return new ControllerParameter<double>(controller, name, PrimitiveType.Double, ParameterContext.Axis, index);case PrimitiveType.Integer:return new ControllerParameter<int>(controller, name, PrimitiveType.Integer, ParameterContext.Axis, index);case PrimitiveType.Long:return new ControllerParameter<long>(controller, name, PrimitiveType.Long, ParameterContext.Axis, index);case PrimitiveType.Single:return new ControllerParameter<float>(controller, name, PrimitiveType.Single, ParameterContext.Axis, index);case PrimitiveType.String:return new ControllerParameter<string>(controller, name, PrimitiveType.String, ParameterContext.Axis, index);default:return null;}
#endif}public Parameter CreateTask(string name, int task){
#if CSHARP_8_OR_NEWERreturn ParameterInfoProvider.GetType(name) switch{PrimitiveType.Double => new ControllerParameter<double>(controller, name, PrimitiveType.Double, ParameterContext.Task, task),PrimitiveType.Integer => new ControllerParameter<int>(controller, name, PrimitiveType.Integer, ParameterContext.Task, task),PrimitiveType.Long => new ControllerParameter<long>(controller, name, PrimitiveType.Long, ParameterContext.Task, task),PrimitiveType.Single => new ControllerParameter<float>(controller, name, PrimitiveType.Single, ParameterContext.Task, task),PrimitiveType.String => new ControllerParameter<string>(controller, name, PrimitiveType.String, ParameterContext.Task, task),_ => null,};
#elsePrimitiveType type = ParameterInfoProvider.GetType(name);switch (type){case PrimitiveType.Double:return new ControllerParameter<double>(controller, name, PrimitiveType.Double, ParameterContext.Task, task);case PrimitiveType.Integer:return new ControllerParameter<int>(controller, name, PrimitiveType.Integer, ParameterContext.Task, task);case PrimitiveType.Long:return new ControllerParameter<long>(controller, name, PrimitiveType.Long, ParameterContext.Task, task);case PrimitiveType.Single:return new ControllerParameter<float>(controller, name, PrimitiveType.Single, ParameterContext.Task, task);case PrimitiveType.String:return new ControllerParameter<string>(controller, name, PrimitiveType.String, ParameterContext.Task, task);default:return null;}
#endif}
}关键实现说明
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条件编译符号
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使用
#if CSHARP_8_OR_NEWER和#else隔离不同版本的语法。 -
需在项目文件中定义符号（见下方配置步骤）。
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版本差异处理
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C# 8.0+：使用简洁的递归模式匹配（
switch表达式）。 -
C# 7.3：回退到传统的
switch-case语句。
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功能一致性
两种写法的逻辑完全一致，仅语法形式不同。
项目配置步骤
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定义编译符号
在.csproj文件中根据语言版本自动设置符号：
<PropertyGroup><!-- 当使用 C# 8.0+ 时自动定义符号 --><DefineConstants Condition="'$(LangVersion)' >= '8.0'">CSHARP_8_OR_NEWER</DefineConstants>
</PropertyGroup> 手动指定版本（可选）
若需强制兼容性，可手动设置语言版本：
<PropertyGroup><LangVersion>7.3</LangVersion> <!-- 或 8.0、latest 等 -->
</PropertyGroup>优点
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无缝适配：根据项目语言版本自动选择最优语法。
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维护友好：升级到 C# 8.0+ 时无需修改代码，直接享受新语法。
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编译安全：避免因版本不兼容导致的编译错误。