Add links to the new conceptual documentation

src/System.CommandLine/Argument.cs

@@ -12,6 +12,8 @@ namespace System.CommandLine
     /// <summary>
     /// A symbol defining a value that can be passed on the command line to a <see cref="Command">command</see> or <see cref="Option">option</see>.
     /// </summary>
+    /// <seealso href="/dotnet/standard/commandline/syntax">Command-line syntax overview</seealso>
+    /// <seealso href="/dotnet/standard/commandline/define-commands">How to define commands, options, and arguments</seealso>
     public abstract class Argument : Symbol, IValueDescriptor
     {
         private Func<ArgumentResult, object?>? _defaultValueFactory;
@@ -23,6 +25,7 @@ public abstract class Argument : Symbol, IValueDescriptor
         /// <summary>
         /// Initializes a new instance of the Argument class.
         /// </summary>
+        /// <seealso href="/dotnet/standard/commandline/define-commands">How to define commands, options, and arguments</seealso>
         protected Argument()
         {
         }
@@ -32,6 +35,7 @@ protected Argument()
         /// </summary>
         /// <param name="name">The name of the argument.</param>
         /// <param name="description">The description of the argument, shown in help.</param>
+        /// <seealso href="/dotnet/standard/commandline/define-commands">How to define commands, options, and arguments</seealso>
         protected Argument(string? name = null, string? description = null)
         {
             Name = name!;
@@ -41,8 +45,9 @@ protected Argument(string? name = null, string? description = null)
         internal HashSet<string>? AllowedValues { get; private set; }
 
         /// <summary>
-        /// Gets or sets the arity of the argument.
+        /// Gets or sets the <see href="/dotnet/standard/commandline/syntax#argument-arity">arity</see> of the argument.
         /// </summary>
+        /// <seealso href="/dotnet/standard/commandline/define-commands">How to define commands, options, and arguments</seealso>
         public ArgumentArity Arity
         {
             get
@@ -63,6 +68,7 @@ public ArgumentArity Arity
         /// <summary>
         /// The name used in help output to describe the argument. 
         /// </summary>
+    /// <seealso href="/dotnet/standard/commandline/customize-help">How to customize help</seealso>
         public string? HelpName { get; set; }
 
         internal TryConvertArgument? ConvertArguments
@@ -83,6 +89,7 @@ internal TryConvertArgument? ConvertArguments
         /// <summary>
         /// Gets or sets the <see cref="Type" /> that the argument token(s) will be converted to.
         /// </summary>
+        /// <seealso href="/dotnet/standard/commandline/define-commands">How to define commands, options, and arguments</seealso>
         public abstract Type ValueType { get; }
 
         private protected override string DefaultName
@@ -111,13 +118,15 @@ private protected override string DefaultName
         /// to provide custom errors based on user input.
         /// </summary>
         /// <param name="validate">The delegate to validate the parsed argument.</param>
+        /// <seealso href="/dotnet/standard/commandline/model-binding#custom-validation-and-binding">How to bind arguments to handlers - Custom validation and binding</seealso>
         public void AddValidator(ValidateSymbolResult<ArgumentResult> validate) => Validators.Add(validate);
 
         /// <summary>
         /// Gets the default value for the argument.
         /// </summary>
         /// <returns>Returns the default value for the argument, if defined. Null otherwise.</returns>
-        public object? GetDefaultValue()
+        /// <seealso href="/dotnet/standard/commandline/define-commands">How to define commands, options, and arguments</seealso>
+       public object? GetDefaultValue()
         {
             return GetDefaultValue(new ArgumentResult(this, null));
         }
@@ -136,6 +145,7 @@ private protected override string DefaultName
         /// Sets the default value for the argument.
         /// </summary>
         /// <param name="value">The default value for the argument.</param>
+        /// <seealso href="/dotnet/standard/commandline/define-commands">How to define commands, options, and arguments</seealso>
         public void SetDefaultValue(object? value)
         {
             SetDefaultValueFactory(() => value);
@@ -146,6 +156,7 @@ public void SetDefaultValue(object? value)
         /// </summary>
         /// <param name="getDefaultValue">The delegate to invoke to return the default value.</param>
         /// <exception cref="ArgumentNullException">Thrown when <paramref name="getDefaultValue"/> is null.</exception>
+        /// <seealso href="/dotnet/standard/commandline/define-commands">How to define commands, options, and arguments</seealso>
         public void SetDefaultValueFactory(Func<object?> getDefaultValue)
         {
             if (getDefaultValue is null)
@@ -161,6 +172,7 @@ public void SetDefaultValueFactory(Func<object?> getDefaultValue)
         /// </summary>
         /// <param name="getDefaultValue">The delegate to invoke to return the default value.</param>
         /// <remarks>In this overload, the <see cref="ArgumentResult"/> is provided to the delegate.</remarks>
+        /// <seealso href="/dotnet/standard/commandline/define-commands">How to define commands, options, and arguments</seealso>
         public void SetDefaultValueFactory(Func<ArgumentResult, object?> getDefaultValue)
         {
             _defaultValueFactory = getDefaultValue ?? throw new ArgumentNullException(nameof(getDefaultValue));
@@ -169,6 +181,7 @@ public void SetDefaultValueFactory(Func<ArgumentResult, object?> getDefaultValue
         /// <summary>
         /// Specifies if a default value is defined for the argument.
         /// </summary>
+        /// <seealso href="/dotnet/standard/commandline/define-commands">How to define commands, options, and arguments</seealso>
         public bool HasDefaultValue => _defaultValueFactory is not null;
 
         internal virtual bool HasCustomParser => false;

src/System.CommandLine/ArgumentArity.cs

@@ -9,10 +9,11 @@
 namespace System.CommandLine
 {
     /// <summary>
-    /// Defines the arity of an option or argument.
+    /// Defines the <see href="/dotnet/standard/commandline/syntax#argument-arity">arity</see> of an option or argument.
     /// </summary>
     /// <remarks>The arity refers to the number of values that can be passed on the command line.
     /// </remarks>
+    /// <seealso href="/dotnet/standard/commandline/syntax">Command-line syntax overview</seealso>
     [DebuggerDisplay("\\{{" + nameof(MinimumNumberOfValues) + "},{" + nameof(MaximumNumberOfValues) + "}\\}")]
     public readonly struct ArgumentArity : IEquatable<ArgumentArity>
     {
@@ -25,6 +26,7 @@ namespace System.CommandLine
         /// <param name="maximumNumberOfValues">The maximum number of values allowed for the argument.</param>
         /// <exception cref="ArgumentOutOfRangeException">Thrown when <paramref name="minimumNumberOfValues"/> is negative.</exception>
         /// <exception cref="ArgumentException">Thrown when the maximum number is less than the minimum number or the maximum number is greater than MaximumArity.</exception>
+        /// <seealso href="/dotnet/standard/commandline/syntax">Command-line syntax overview</seealso>
         public ArgumentArity(int minimumNumberOfValues, int maximumNumberOfValues)
         {
             if (minimumNumberOfValues < 0)
@@ -50,11 +52,13 @@ public ArgumentArity(int minimumNumberOfValues, int maximumNumberOfValues)
         /// <summary>
         /// Gets the minimum number of values required for an <see cref="Argument">argument</see>.
         /// </summary>
+        /// <seealso href="/dotnet/standard/commandline/syntax">Command-line syntax overview</seealso>
         public int MinimumNumberOfValues { get; }
 
         /// <summary>
         /// Gets the maximum number of values allowed for an <see cref="Argument">argument</see>.
         /// </summary>
+        /// <seealso href="/dotnet/standard/commandline/syntax">Command-line syntax overview</seealso>
         public int MaximumNumberOfValues { get; }
 
         internal bool IsNonDefault { get;  }
@@ -119,26 +123,31 @@ public override int GetHashCode()
         /// <summary>
         /// An arity that does not allow any values.
         /// </summary>
+        /// <seealso href="/dotnet/standard/commandline/syntax">Command-line syntax overview</seealso>
         public static ArgumentArity Zero => new(0, 0);
 
         /// <summary>
         /// An arity that may have one value, but no more than one.
         /// </summary>
+        /// <seealso href="/dotnet/standard/commandline/syntax">Command-line syntax overview</seealso>
         public static ArgumentArity ZeroOrOne => new(0, 1);
 
         /// <summary>
         /// An arity that must have exactly one value.
         /// </summary>
+        /// <seealso href="/dotnet/standard/commandline/syntax">Command-line syntax overview</seealso>
         public static ArgumentArity ExactlyOne => new(1, 1);
 
         /// <summary>
         /// An arity that may have multiple values.
         /// </summary>
+        /// <seealso href="/dotnet/standard/commandline/syntax">Command-line syntax overview</seealso>
         public static ArgumentArity ZeroOrMore => new(0, MaximumArity);
 
         /// <summary>
         /// An arity that must have at least one value.
         /// </summary>
+        /// <seealso href="/dotnet/standard/commandline/syntax">Command-line syntax overview</seealso>
         public static ArgumentArity OneOrMore => new(1, MaximumArity);
 
         internal static ArgumentArity Default(Type type, Argument argument, ParentNode? firstParent)

src/System.CommandLine/ArgumentExtensions.cs

@@ -11,6 +11,8 @@ namespace System.CommandLine
     /// <summary>
     /// Provides extension methods for <see cref="Argument" />.
     /// </summary>
+    /// <seealso href="/dotnet/standard/commandline/syntax">Command-line syntax overview</seealso>
+    /// <seealso href="/dotnet/standard/commandline/define-commands">How to define commands, options, and arguments</seealso>
     public static class ArgumentExtensions
     {
         /// <summary>
@@ -20,6 +22,7 @@ public static class ArgumentExtensions
         /// <param name="argument">The argument for which to add completions.</param>
         /// <param name="values">The completions to add.</param>
         /// <returns>The configured argument.</returns>
+        /// <seealso href="/dotnet/standard/commandline/tab-completion">Tab completion</seealso>
         public static TArgument AddCompletions<TArgument>(
             this TArgument argument,
             params string[] values)
@@ -37,6 +40,7 @@ public static TArgument AddCompletions<TArgument>(
         /// <param name="argument">The argument for which to add completions.</param>
         /// <param name="complete">A <see cref="CompletionDelegate"/> that will be called to provide completions.</param>
         /// <returns>The option being extended.</returns>
+        /// <seealso href="/dotnet/standard/commandline/tab-completion">Tab completion</seealso>
         public static TArgument AddCompletions<TArgument>(
             this TArgument argument,
             Func<CompletionContext, IEnumerable<string>> complete)
@@ -54,6 +58,7 @@ public static TArgument AddCompletions<TArgument>(
         /// <param name="argument">The argument for which to add completions.</param>
         /// <param name="complete">A <see cref="CompletionDelegate"/> that will be called to provide completions.</param>
         /// <returns>The configured argument.</returns>
+        /// <seealso href="/dotnet/standard/commandline/tab-completion">Tab completion</seealso>
         public static TArgument AddCompletions<TArgument>(
             this TArgument argument,
             CompletionDelegate complete)
@@ -71,6 +76,8 @@ public static TArgument AddCompletions<TArgument>(
         /// <param name="values">The values that are allowed for the argument.</param>
         /// <typeparam name="TArgument">The type of the argument.</typeparam>
         /// <returns>The configured argument.</returns>
+        /// <seealso href="/dotnet/standard/commandline/define-commands">How to define commands, options, and arguments</seealso>
+        /// <seealso href="/dotnet/standard/commandline/tab-completion">Tab completion</seealso>
         public static TArgument FromAmong<TArgument>(
             this TArgument argument,
             params string[] values)
@@ -87,6 +94,7 @@ public static TArgument FromAmong<TArgument>(
         /// </summary>
         /// <param name="argument">The argument to configure.</param>
         /// <returns>The configured argument.</returns>
+        /// <seealso href="/dotnet/standard/commandline/model-binding">How to bind arguments to handlers</seealso>
         public static Argument<FileInfo> ExistingOnly(this Argument<FileInfo> argument)
         {
             argument.AddValidator(Validate.FileExists);
@@ -98,6 +106,7 @@ public static Argument<FileInfo> ExistingOnly(this Argument<FileInfo> argument)
         /// </summary>
         /// <param name="argument">The argument to configure.</param>
         /// <returns>The configured argument.</returns>
+        /// <seealso href="/dotnet/standard/commandline/model-binding">How to bind arguments to handlers</seealso>
         public static Argument<DirectoryInfo> ExistingOnly(this Argument<DirectoryInfo> argument)
         {
             argument.AddValidator(Validate.DirectoryExists);
@@ -109,6 +118,7 @@ public static Argument<DirectoryInfo> ExistingOnly(this Argument<DirectoryInfo>
         /// </summary>
         /// <param name="argument">The argument to configure.</param>
         /// <returns>The configured argument.</returns>
+        /// <seealso href="/dotnet/standard/commandline/model-binding">How to bind arguments to handlers</seealso>
         public static Argument<FileSystemInfo> ExistingOnly(this Argument<FileSystemInfo> argument)
         {
             argument.AddValidator(Validate.FileOrDirectoryExists);
@@ -120,6 +130,7 @@ public static Argument<FileSystemInfo> ExistingOnly(this Argument<FileSystemInfo
         /// </summary>
         /// <param name="argument">The argument to configure.</param>
         /// <returns>The configured argument.</returns>
+        /// <seealso href="/dotnet/standard/commandline/model-binding">How to bind arguments to handlers</seealso>
         public static Argument<T> ExistingOnly<T>(this Argument<T> argument)
             where T : IEnumerable<FileSystemInfo>
         {
@@ -144,6 +155,7 @@ public static Argument<T> ExistingOnly<T>(this Argument<T> argument)
         /// </summary>
         /// <param name="argument">The argument to configure.</param>
         /// <returns>The configured argument.</returns>
+        /// <seealso href="/dotnet/standard/commandline/model-binding">How to bind arguments to handlers</seealso>
         public static TArgument LegalFilePathsOnly<TArgument>(
             this TArgument argument)
             where TArgument : Argument
@@ -176,6 +188,7 @@ public static TArgument LegalFilePathsOnly<TArgument>(
         /// <remarks>A parse error will result, for example, if file path separators are found in the parsed value.</remarks>
         /// <param name="argument">The argument to configure.</param>
         /// <returns>The configured argument.</returns>
+        /// <seealso href="/dotnet/standard/commandline/model-binding">How to bind arguments to handlers</seealso>
         public static TArgument LegalFileNamesOnly<TArgument>(
             this TArgument argument)
             where TArgument : Argument
@@ -206,6 +219,7 @@ public static TArgument LegalFileNamesOnly<TArgument>(
         /// <param name="argument">The argument to use to parse the command line input.</param>
         /// <param name="commandLine">A command line string to parse, which can include spaces and quotes equivalent to what can be entered into a terminal.</param>
         /// <returns>A parse result describing the outcome of the parse operation.</returns>
+        /// <seealso href="/dotnet/standard/commandline/syntax#directives">Command-line syntax overview - Directives</seealso>
         public static ParseResult Parse(
             this Argument argument,
             string commandLine) =>
@@ -217,6 +231,7 @@ public static ParseResult Parse(
         /// <param name="argument">The argument to use to parse the command line input.</param>
         /// <param name="args">The string arguments to parse.</param>
         /// <returns>A parse result describing the outcome of the parse operation.</returns>
+        /// <seealso href="/dotnet/standard/commandline/syntax#directives">Command-line syntax overview - Directives</seealso>
         public static ParseResult Parse(
             this Argument argument,
             string[] args) =>

src/System.CommandLine/Argument{T}.cs

@@ -14,6 +14,7 @@ public class Argument<T> : Argument, IValueDescriptor<T>
         /// <summary>
         /// Initializes a new instance of the Argument class.
         /// </summary>
+        /// <seealso href="/dotnet/standard/commandline/define-commands">How to define commands, options, and arguments</seealso>
         public Argument()
         {
         }
@@ -32,6 +33,7 @@ public Argument(
         /// <param name="getDefaultValue">The delegate to invoke to return the default value.</param>
         /// <param name="description">The description of the argument, shown in help.</param>
         /// <exception cref="ArgumentNullException">Thrown when <paramref name="getDefaultValue"/> is null.</exception>
+        /// <seealso href="/dotnet/standard/commandline/define-commands">How to define commands, options, and arguments</seealso>
         public Argument(
             string name, 
             Func<T> getDefaultValue, 
@@ -50,6 +52,7 @@ public Argument(
         /// </summary>
         /// <param name="getDefaultValue">The delegate to invoke to return the default value.</param>
         /// <exception cref="ArgumentNullException">Thrown when <paramref name="getDefaultValue"/> is null.</exception>
+        /// <seealso href="/dotnet/standard/commandline/define-commands">How to define commands, options, and arguments</seealso>
         public Argument(Func<T> getDefaultValue) : this()
         {
             if (getDefaultValue is null)
@@ -68,6 +71,7 @@ public Argument(Func<T> getDefaultValue) : this()
         /// <param name="isDefault"><see langword="true"/> to use the <paramref name="parse"/> result as default value.</param>
         /// <param name="description">The description of the argument, shown in help.</param>
         /// <exception cref="ArgumentNullException">Thrown when <paramref name="parse"/> is null.</exception>
+        /// <seealso href="/dotnet/standard/commandline/define-commands">How to define commands, options, and arguments</seealso>
         public Argument(
             string? name,
             ParseArgument<T> parse, 
@@ -108,6 +112,7 @@ public Argument(
         /// </summary>
         /// <param name="parse">A custom argument parser.</param>
         /// <param name="isDefault"><see langword="true"/> to use the <paramref name="parse"/> result as default value.</param>
+        /// <seealso href="/dotnet/standard/commandline/define-commands">How to define commands, options, and arguments</seealso>
         public Argument(ParseArgument<T> parse, bool isDefault = false) : this(null!, parse, isDefault)
         {
         }

src/System.CommandLine/Binding/BinderBase{T}.cs

@@ -4,6 +4,8 @@
 /// Supports binding of custom types.
 /// </summary>
 /// <typeparam name="T">The type to be bound.</typeparam>
+/// <seealso href="/dotnet/standard/commandline/model-binding#model-binding-more-than-16-options-and-arguments">Model binding more than 16 options and arguments</seealso>
+
 public abstract class BinderBase<T> :
     IValueDescriptor<T>,
     IValueSource
@@ -13,6 +15,7 @@ public abstract class BinderBase<T> :
     /// </summary>
     /// <param name="bindingContext"></param>
     /// <returns></returns>
+    /// <seealso href="/dotnet/standard/commandline/model-binding#model-binding-more-than-16-options-and-arguments">Model binding more than 16 options and arguments</seealso>
     protected abstract T GetBoundValue(BindingContext bindingContext);
 
     string IValueDescriptor.ValueName => GetType().Name;