OpCodes.Switch Field


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Implements a jump table.

Namespace:   System.Reflection.Emit
Assembly:  mscorlib (in mscorlib.dll)

static val Switch : OpCode

The following table lists the instruction's hexadecimal and Microsoft Intermediate Language (MSIL) assembly format, along with a brief reference summary:


Assembly Format


45 < unsigned int32 > < int32 >... < int32 >

switch (N, t1, t2... tN)

Jumps to one of N values.

The stack transitional behavior, in sequential order, is:

  1. A value is pushed onto the stack.

  2. The value is popped off the stack and execution is transferred to the instruction at the offset indexed by the value, where the value is less than N.

The switch instruction implements a jump table. The format of the instruction is an unsigned int32 representing the number of targets N, followed by N int32 values specifying jump targets. These targets are represented as offsets (positive or negative) from the beginning of the instruction following this switch instruction.

The switch instruction pops a value off the stack and compares it, as an unsigned integer, to N. If value is less than N, execution is transferred to the target indexed by value, where targets are numbered from 0 (for example, a value of 0 takes the first target, a value of 1 takes the second target, and so on). If the value is greater than or equal to N, execution continues at the next instruction (fall through).

If the target instruction has one or more prefix codes, control can only be transferred to the first of these prefixes.

Control transfers into and out of try, catch, filter, and finally blocks cannot be performed by this instruction. (Such transfers are severely restricted and must use the leave instruction instead).

The following Emit method overload can use the switch opcode. The Label[] argument is an array of Labels representing 32-bit offsets.

  • ILGenerator.Emit(OpCode, Label[])

The following code sample illustrates the use of the Switch opcode to generate a jump table using an array of Label.

No code example is currently available or this language may not be supported.

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.1
Windows Phone
Available since 8.1
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