Expression.Switch 方法

参考

定义

命名空间:: System.Linq.Expressions

程序集:: System.Linq.Expressions.dll

程序集:: System.Core.dll

程序集:: netstandard.dll

重要

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创建一个表示 SwitchExpression 语句的 switch。

重载

Switch(Type, Expression, Expression, MethodInfo, SwitchCase[])	创建一个表示具有默认分支的 SwitchExpression 语句的 `switch`。
Switch(Expression, SwitchCase[])	创建一个表示不带默认分支的 SwitchExpression 语句的 `switch`。
Switch(Expression, Expression, SwitchCase[])	创建一个表示具有默认分支的 SwitchExpression 语句的 `switch`。
Switch(Expression, Expression, MethodInfo, IEnumerable<SwitchCase>)	创建一个表示具有默认分支的 SwitchExpression 语句的 `switch`。
Switch(Expression, Expression, MethodInfo, SwitchCase[])	创建一个表示具有默认分支的 SwitchExpression 语句的 `switch`。
Switch(Type, Expression, Expression, MethodInfo, IEnumerable<SwitchCase>)	创建一个表示具有默认分支的 SwitchExpression 语句的 `switch`。

Switch(Type, Expression, Expression, MethodInfo, SwitchCase[])

Source:: SwitchExpression.cs

Source:: SwitchExpression.cs

Source:: SwitchExpression.cs

创建一个表示具有默认分支的 SwitchExpression 语句的 switch。

public:
 static System::Linq::Expressions::SwitchExpression ^ Switch(Type ^ type, System::Linq::Expressions::Expression ^ switchValue, System::Linq::Expressions::Expression ^ defaultBody, System::Reflection::MethodInfo ^ comparison, ... cli::array <System::Linq::Expressions::SwitchCase ^> ^ cases);

public static System.Linq.Expressions.SwitchExpression Switch (Type type, System.Linq.Expressions.Expression switchValue, System.Linq.Expressions.Expression defaultBody, System.Reflection.MethodInfo comparison, params System.Linq.Expressions.SwitchCase[] cases);

public static System.Linq.Expressions.SwitchExpression Switch (Type? type, System.Linq.Expressions.Expression switchValue, System.Linq.Expressions.Expression? defaultBody, System.Reflection.MethodInfo? comparison, params System.Linq.Expressions.SwitchCase[]? cases);

static member Switch : Type * System.Linq.Expressions.Expression * System.Linq.Expressions.Expression * System.Reflection.MethodInfo * System.Linq.Expressions.SwitchCase[] -> System.Linq.Expressions.SwitchExpression

Public Shared Function Switch (type As Type, switchValue As Expression, defaultBody As Expression, comparison As MethodInfo, ParamArray cases As SwitchCase()) As SwitchExpression

参数

type: Type

switch 的结果类型。

switchValue: Expression

要针对每个分支测试的值。

defaultBody: Expression

switchValue 不匹配任何分支时，该 switch 的结果。

comparison: MethodInfo

要使用的相等比较方法。

cases: SwitchCase[]

此 switch 表达式的分支集。

SwitchExpression

创建的 SwitchExpression。

适用于

Switch(Expression, SwitchCase[])

Source:: SwitchExpression.cs

Source:: SwitchExpression.cs

Source:: SwitchExpression.cs

创建一个表示不带默认分支的 SwitchExpression 语句的 switch。

public:
 static System::Linq::Expressions::SwitchExpression ^ Switch(System::Linq::Expressions::Expression ^ switchValue, ... cli::array <System::Linq::Expressions::SwitchCase ^> ^ cases);

public static System.Linq.Expressions.SwitchExpression Switch (System.Linq.Expressions.Expression switchValue, params System.Linq.Expressions.SwitchCase[] cases);

public static System.Linq.Expressions.SwitchExpression Switch (System.Linq.Expressions.Expression switchValue, params System.Linq.Expressions.SwitchCase[]? cases);

static member Switch : System.Linq.Expressions.Expression * System.Linq.Expressions.SwitchCase[] -> System.Linq.Expressions.SwitchExpression

Public Shared Function Switch (switchValue As Expression, ParamArray cases As SwitchCase()) As SwitchExpression

参数

switchValue: Expression

要针对每个分支测试的值。

cases: SwitchCase[]

此 switch 表达式的分支集。

SwitchExpression

创建的 SwitchExpression。

示例

以下示例演示如何创建一个表达式，该表达式表示不带默认大小写的 switch 语句。

// Add the following directive to the file:
// using System.Linq.Expressions;

// An expression that represents the switch value.
ConstantExpression switchValue = Expression.Constant(2);

// This expression represents a switch statement
// without a default case.
SwitchExpression switchExpr =
    Expression.Switch(
        switchValue,
        new SwitchCase[] {
            Expression.SwitchCase(
                Expression.Call(
                    null,
                    typeof(Console).GetMethod("WriteLine", new Type[] { typeof(String) }),
                    Expression.Constant("First")
                ),
                Expression.Constant(1)
            ),
            Expression.SwitchCase(
                Expression.Call(
                    null,
                    typeof(Console).GetMethod("WriteLine", new Type[] { typeof(String) }),
                    Expression.Constant("Second")
                ),
                Expression.Constant(2)
            )
        }
    );

// The following statement first creates an expression tree,
// then compiles it, and then runs it.
Expression.Lambda<Action>(switchExpr).Compile()();

// This code example produces the following output:
//
// Second

' Add the following directive to the file:
' Imports System.Linq.Expressions

' An expression that represents the switch value.
Dim switchValue As ConstantExpression = Expression.Constant(2)

' This expression represents a switch statement 
' without a default case.
Dim switchExpr As SwitchExpression =
Expression.Switch(
    switchValue,
    New SwitchCase() {
        Expression.SwitchCase(
            Expression.Call(
                Nothing,
                GetType(Console).GetMethod("WriteLine", New Type() {GetType(String)}),
                Expression.Constant("First")
            ),
            Expression.Constant(1)
        ),
        Expression.SwitchCase(
            Expression.Call(
                Nothing,
                GetType(Console).GetMethod("WriteLine", New Type() {GetType(String)}),
                Expression.Constant("Second")
            ),
            Expression.Constant(2)
        )
    }
)

' The following statement first creates an expression tree,
' then compiles it, and then runs it.
Expression.Lambda(Of Action)(switchExpr).Compile()()

' This code example produces the following output:
'
' Second

注解

SwitchCase对象中的所有SwitchExpression对象必须具有相同的类型，除非 SwitchExpression 的类型为 void。

每个对象都有 SwitchCase 一个隐式 break 语句，这意味着不存在从一个事例标签到另一个事例标签的隐式下降。

如果 switchValue 与任何情况不匹配，则不会引发异常。

适用于

Switch(Expression, Expression, SwitchCase[])

Source:: SwitchExpression.cs

Source:: SwitchExpression.cs

Source:: SwitchExpression.cs

创建一个表示具有默认分支的 SwitchExpression 语句的 switch。

public:
 static System::Linq::Expressions::SwitchExpression ^ Switch(System::Linq::Expressions::Expression ^ switchValue, System::Linq::Expressions::Expression ^ defaultBody, ... cli::array <System::Linq::Expressions::SwitchCase ^> ^ cases);

public static System.Linq.Expressions.SwitchExpression Switch (System.Linq.Expressions.Expression switchValue, System.Linq.Expressions.Expression defaultBody, params System.Linq.Expressions.SwitchCase[] cases);

public static System.Linq.Expressions.SwitchExpression Switch (System.Linq.Expressions.Expression switchValue, System.Linq.Expressions.Expression? defaultBody, params System.Linq.Expressions.SwitchCase[]? cases);

static member Switch : System.Linq.Expressions.Expression * System.Linq.Expressions.Expression * System.Linq.Expressions.SwitchCase[] -> System.Linq.Expressions.SwitchExpression

Public Shared Function Switch (switchValue As Expression, defaultBody As Expression, ParamArray cases As SwitchCase()) As SwitchExpression

参数

switchValue: Expression

要针对每个分支测试的值。

defaultBody: Expression

switchValue 不匹配任何分支时，该 switch 的结果。

cases: SwitchCase[]

此 switch 表达式的分支集。

SwitchExpression

创建的 SwitchExpression。

示例

以下示例演示如何创建表示具有默认事例的 switch 语句的表达式。

// Add the following directive to the file:
// using System.Linq.Expressions;

// An expression that represents the switch value.
ConstantExpression switchValue = Expression.Constant(3);

// This expression represents a switch statement
// that has a default case.
SwitchExpression switchExpr =
    Expression.Switch(
        switchValue,
        Expression.Call(
                    null,
                    typeof(Console).GetMethod("WriteLine", new Type[] { typeof(String) }),
                    Expression.Constant("Default")
                ),
        new SwitchCase[] {
            Expression.SwitchCase(
                Expression.Call(
                    null,
                    typeof(Console).GetMethod("WriteLine", new Type[] { typeof(String) }),
                    Expression.Constant("First")
                ),
                Expression.Constant(1)
            ),
            Expression.SwitchCase(
                Expression.Call(
                    null,
                    typeof(Console).GetMethod("WriteLine", new Type[] { typeof(String) }),
                    Expression.Constant("Second")
                ),
                Expression.Constant(2)
            )
        }
    );

// The following statement first creates an expression tree,
// then compiles it, and then runs it.
Expression.Lambda<Action>(switchExpr).Compile()();

// This code example produces the following output:
//
// Default

' Add the following directive to the file:
' Imports System.Linq.Expressions

' An expression that represents the switch value.
Dim switchValue As ConstantExpression = Expression.Constant(3)

' This expression represents a switch statement 
' that has a default case.
Dim switchExpr As SwitchExpression =
Expression.Switch(
    switchValue,
    Expression.Call(
                Nothing,
                GetType(Console).GetMethod("WriteLine", New Type() {GetType(String)}),
                Expression.Constant("Default")
            ),
    New SwitchCase() {
        Expression.SwitchCase(
            Expression.Call(
                Nothing,
                GetType(Console).GetMethod("WriteLine", New Type() {GetType(String)}),
                Expression.Constant("First")
            ),
            Expression.Constant(1)
        ),
        Expression.SwitchCase(
            Expression.Call(
                Nothing,
                GetType(Console).GetMethod("WriteLine", New Type() {GetType(String)}),
                Expression.Constant("Second")
            ),
            Expression.Constant(2)
        )
    }
)

' The following statement first creates an expression tree,
' then compiles it, and then runs it.
Expression.Lambda(Of Action)(switchExpr).Compile()()

' This code example produces the following output:
'
' Default

注解

SwitchCase对象中的所有SwitchExpression对象必须具有相同的类型，除非 SwitchExpression 的类型为 void。

每个对象都有 SwitchCase 一个隐式 break 语句，这意味着不存在从一个事例标签到另一个事例标签的隐式下降。

如果 switchValue 与任何事例不匹配，则运行由 defaultBody 表示的默认事例。

适用于

Switch(Expression, Expression, MethodInfo, IEnumerable<SwitchCase>)

Source:: SwitchExpression.cs

Source:: SwitchExpression.cs

Source:: SwitchExpression.cs

创建一个表示具有默认分支的 SwitchExpression 语句的 switch。

public:
 static System::Linq::Expressions::SwitchExpression ^ Switch(System::Linq::Expressions::Expression ^ switchValue, System::Linq::Expressions::Expression ^ defaultBody, System::Reflection::MethodInfo ^ comparison, System::Collections::Generic::IEnumerable<System::Linq::Expressions::SwitchCase ^> ^ cases);

public static System.Linq.Expressions.SwitchExpression Switch (System.Linq.Expressions.Expression switchValue, System.Linq.Expressions.Expression defaultBody, System.Reflection.MethodInfo comparison, System.Collections.Generic.IEnumerable<System.Linq.Expressions.SwitchCase> cases);

public static System.Linq.Expressions.SwitchExpression Switch (System.Linq.Expressions.Expression switchValue, System.Linq.Expressions.Expression? defaultBody, System.Reflection.MethodInfo? comparison, System.Collections.Generic.IEnumerable<System.Linq.Expressions.SwitchCase>? cases);

static member Switch : System.Linq.Expressions.Expression * System.Linq.Expressions.Expression * System.Reflection.MethodInfo * seq<System.Linq.Expressions.SwitchCase> -> System.Linq.Expressions.SwitchExpression

Public Shared Function Switch (switchValue As Expression, defaultBody As Expression, comparison As MethodInfo, cases As IEnumerable(Of SwitchCase)) As SwitchExpression

参数

switchValue: Expression

要针对每个分支测试的值。

defaultBody: Expression

switchValue 不匹配任何分支时，该 switch 的结果。

comparison: MethodInfo

要使用的相等比较方法。

cases: IEnumerable<SwitchCase>

此 switch 表达式的分支集。

SwitchExpression

创建的 SwitchExpression。

适用于

Switch(Expression, Expression, MethodInfo, SwitchCase[])

Source:: SwitchExpression.cs

Source:: SwitchExpression.cs

Source:: SwitchExpression.cs

创建一个表示具有默认分支的 SwitchExpression 语句的 switch。

public:
 static System::Linq::Expressions::SwitchExpression ^ Switch(System::Linq::Expressions::Expression ^ switchValue, System::Linq::Expressions::Expression ^ defaultBody, System::Reflection::MethodInfo ^ comparison, ... cli::array <System::Linq::Expressions::SwitchCase ^> ^ cases);

public static System.Linq.Expressions.SwitchExpression Switch (System.Linq.Expressions.Expression switchValue, System.Linq.Expressions.Expression defaultBody, System.Reflection.MethodInfo comparison, params System.Linq.Expressions.SwitchCase[] cases);

public static System.Linq.Expressions.SwitchExpression Switch (System.Linq.Expressions.Expression switchValue, System.Linq.Expressions.Expression? defaultBody, System.Reflection.MethodInfo? comparison, params System.Linq.Expressions.SwitchCase[]? cases);

static member Switch : System.Linq.Expressions.Expression * System.Linq.Expressions.Expression * System.Reflection.MethodInfo * System.Linq.Expressions.SwitchCase[] -> System.Linq.Expressions.SwitchExpression

Public Shared Function Switch (switchValue As Expression, defaultBody As Expression, comparison As MethodInfo, ParamArray cases As SwitchCase()) As SwitchExpression

参数

switchValue: Expression

要针对每个分支测试的值。

defaultBody: Expression

switchValue 不匹配任何分支时，该 switch 的结果。

comparison: MethodInfo

要使用的相等比较方法。

cases: SwitchCase[]

此 switch 表达式的分支集。

SwitchExpression

创建的 SwitchExpression。

适用于

Switch(Type, Expression, Expression, MethodInfo, IEnumerable<SwitchCase>)

Source:: SwitchExpression.cs

Source:: SwitchExpression.cs

Source:: SwitchExpression.cs

创建一个表示具有默认分支的 SwitchExpression 语句的 switch。

public:
 static System::Linq::Expressions::SwitchExpression ^ Switch(Type ^ type, System::Linq::Expressions::Expression ^ switchValue, System::Linq::Expressions::Expression ^ defaultBody, System::Reflection::MethodInfo ^ comparison, System::Collections::Generic::IEnumerable<System::Linq::Expressions::SwitchCase ^> ^ cases);

public static System.Linq.Expressions.SwitchExpression Switch (Type type, System.Linq.Expressions.Expression switchValue, System.Linq.Expressions.Expression defaultBody, System.Reflection.MethodInfo comparison, System.Collections.Generic.IEnumerable<System.Linq.Expressions.SwitchCase> cases);

public static System.Linq.Expressions.SwitchExpression Switch (Type? type, System.Linq.Expressions.Expression switchValue, System.Linq.Expressions.Expression? defaultBody, System.Reflection.MethodInfo? comparison, System.Collections.Generic.IEnumerable<System.Linq.Expressions.SwitchCase>? cases);

static member Switch : Type * System.Linq.Expressions.Expression * System.Linq.Expressions.Expression * System.Reflection.MethodInfo * seq<System.Linq.Expressions.SwitchCase> -> System.Linq.Expressions.SwitchExpression

Public Shared Function Switch (type As Type, switchValue As Expression, defaultBody As Expression, comparison As MethodInfo, cases As IEnumerable(Of SwitchCase)) As SwitchExpression

参数

type: Type

switch 的结果类型。

switchValue: Expression

要针对每个分支测试的值。

defaultBody: Expression

switchValue 不匹配任何分支时，该 switch 的结果。

comparison: MethodInfo

要使用的相等比较方法。

cases: IEnumerable<SwitchCase>

此 switch 表达式的分支集。

SwitchExpression

创建的 SwitchExpression。

适用于

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通过

Switch(Type, Expression, Expression, MethodInfo, SwitchCase[])

参数

返回

适用于

Switch(Expression, SwitchCase[])

参数

返回

示例

注解

适用于

Switch(Expression, Expression, SwitchCase[])

参数

返回

示例

注解

适用于

Switch(Expression, Expression, MethodInfo, IEnumerable<SwitchCase>)

参数

返回

适用于

Switch(Expression, Expression, MethodInfo, SwitchCase[])

参数

返回

适用于

Switch(Type, Expression, Expression, MethodInfo, IEnumerable<SwitchCase>)

参数

返回

适用于