Parallel.For Method (Int32, Int32, Action<Int32>)

.NET Framework (current version)

Executes a for (For in Visual Basic) loop in which iterations may run in parallel.

Namespace:   System.Threading.Tasks
Assembly:  mscorlib (in mscorlib.dll)

static member For : 
        fromInclusive:int *
        toExclusive:int *
        body:Action<int> -> ParallelLoopResult


Type: System.Int32

The start index, inclusive.

Type: System.Int32

The end index, exclusive.

Type: System.Action<Int32>

The delegate that is invoked once per iteration.

Return Value

Type: System.Threading.Tasks.ParallelLoopResult

A structure that contains information about which portion of the loop completed.

Exception Condition

The body argument is null.


The exception that contains all the individual exceptions thrown on all threads.

The body delegate is invoked once for each value in the iteration range (fromInclusive, toExclusive). It is provided with the iteration count (Int32) as a parameter.

If fromInclusive is greater than or equal to toExclusive, the method returns immediately without performing any iterations.

The following example uses the For method for 100 invocations of a delegate that generates random byte values and computes their sum.

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

Universal Windows Platform
Available since 8
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Windows Phone
Available since 8.1
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