如何为System.CommandLine同一选项传递多个值？

初始问题 #

我想给C#控制台应用传递多个数字，代码示例如下：

private const long DEFAULT_ALPHA_VALUE = 1234567890L;
private static long[] alphas = { DEFAULT_ALPHA_VALUE };

public static async Task Main()
{
    Option<long[]> alphaOption = new
    (
        aliases: new[] { "-a", "--alpha" },
        getDefaultValue: () => new[] { DEFAULT_ALPHA_VALUE },
        description: "Numerical alpha values"
    );

    RootCommand rootCommand = new("A test app for multiple numerical values option");
    rootCommand.AddGlobalOption(alphaOption);
    rootCommand.SetHandler(a => { alphas = a; }, alphaOption);
    
    await RunInvokeAsync(rootCommand, "-a", "1234");
    await RunInvokeAsync(rootCommand, "-a", "1234", "5678"); // 错误：Unrecognized command or argument '5678'.
    await RunInvokeAsync(rootCommand, "-a", "1234 5678"); // 错误：Cannot parse argument '1234 5678' for option '-a' as expected type 'System.Int64'.
    await RunInvokeAsync(rootCommand, "-a", "1234,5678"); // 错误：Cannot parse argument '1234,5678' for option '-a' as expected type 'System.Int64'.
}

private static async Task RunInvokeAsync(RootCommand rootCommand, params string[] args)
{
    int status = await rootCommand.InvokeAsync(args);
    Console.WriteLine($"args: {JsonSerializer.Serialize(args)}, status: {status}, alphas: {JsonSerializer.Serialize(alphas)}");
}

我期望用以下任意一种命令传递多个数字：

dotnet run --project MultipleValuesOption.csproj -- -a 1234 5678
dotnet run --project MultipleValuesOption.csproj -- -a 1234,5678

但运行时均出现错误，请问该如何正确传递多个数字？是代码逻辑有问题，还是调用方式不对？

更新后的问题 #

按照建议给选项添加了AllowMultipleArgumentsPerToken = true，但新增第二个选项后，参数仍未被正确读取。代码示例：

private const long DEFAULT_ALPHA_VALUE = 13579L;
private static long[] alphas = { DEFAULT_ALPHA_VALUE };
private const long DEFAULT_BETA_VALUE = 24680L;
private static long[] betas = { DEFAULT_BETA_VALUE };

public static async Task Main(string[] args)
{
    Option<long[]> alphaOption = new
    (
        aliases: new[] { "-a", "--alpha" },
        getDefaultValue: () => new[] { DEFAULT_ALPHA_VALUE },
        description: "Numerical alpha values"
    )
    { 
        AllowMultipleArgumentsPerToken = true,
    };

    Option<long[]> betaOption = new
    (
        aliases: new[] { "-b", "--beta" },
        getDefaultValue: () => new[] { DEFAULT_BETA_VALUE },
        description: "Numerical beta values"
    )
    {
        AllowMultipleArgumentsPerToken = true,
    };

    RootCommand rootCommand = new("A test app for multiple numerical values option");
    rootCommand.AddGlobalOption(alphaOption);
    rootCommand.AddGlobalOption(betaOption);
    rootCommand.SetHandler(a => { alphas = a; }, alphaOption);
    rootCommand.SetHandler(b => { betas = b; }, betaOption);

    await RunInvokeAsync(rootCommand, args);
    await RunInvokeAsync(rootCommand, "-a", "1234", "5678");
}

private static async Task RunInvokeAsync(RootCommand rootCommand, params string[] args)
{
    int status = await rootCommand.InvokeAsync(args);
    Console.WriteLine($"args: {JsonSerializer.Serialize(args)}, status: {status}, alphas: {JsonSerializer.Serialize(alphas)}, betas: {JsonSerializer.Serialize(betas)}");
}

输出显示alphas始终保持默认值13579，没有读取命令行传入的参数：

args: [], status: 0, alphas: [13579], betas: [24680]
args: ["-a","1234","5678"], status: 0, alphas: [13579], betas: [24680]

解决方案 #

1. 单选项多参数的正确配置 #

要支持-a 1234 5678这种空格分隔的多参数传递，需要为Option<long[]>配置两个关键属性：

• AllowMultipleArgumentsPerToken = true：允许一个选项令牌后跟随多个参数值
• Arity = ArgumentArity.ZeroOrMore：明确参数可以是0个或多个（数组类型默认已隐含，但显式设置更清晰）

修改后的单个选项代码：

Option<long[]> alphaOption = new(
    aliases: new[] { "-a", "--alpha" },
    getDefaultValue: () => new[] { DEFAULT_ALPHA_VALUE },
    description: "Numerical alpha values"
)
{
    AllowMultipleArgumentsPerToken = true,
    Arity = ArgumentArity.ZeroOrMore
};

此时使用dotnet run -- -a 1234 5678即可正确传递多个数字。

2. 多选项时的处理器绑定问题 #

你遇到的第二个问题是因为多次调用SetHandler会覆盖之前的处理器，RootCommand只能有一个主处理器。正确做法是创建一个包含所有选项参数的处理器，一次性绑定所有选项：

// 替换原来的两次SetHandler调用
rootCommand.SetHandler((a, b) => 
{
    alphas = a;
    betas = b;
}, alphaOption, betaOption);

这样就能同时读取-a和-b的参数值。

3. 支持逗号分隔的参数（可选） #

如果想同时支持-a 1234,5678这种逗号分隔的格式，需要自定义参数解析器：

Option<long[]> alphaOption = new(
    aliases: new[] { "-a", "--alpha" },
    parseArgument: (context, value) => 
    {
        // 分割逗号并转换为long数组
        return value.Split(',', StringSplitOptions.RemoveEmptyEntries)
                    .Select(long.Parse)
                    .ToArray();
    },
    getDefaultValue: () => new[] { DEFAULT_ALPHA_VALUE },
    description: "Numerical alpha values"
)
{
    AllowMultipleArgumentsPerToken = true,
    Arity = ArgumentArity.ZeroOrMore
};

此时两种传递方式-a 1234 5678和-a 1234,5678都能生效。

内容的提问来源于stack exchange，提问作者Alexander Farber