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Strings.InStr Method (Int32, String, String, CompareMethod)

Returns an integer specifying the start position of the first occurrence of one string within another.

Namespace:  Microsoft.VisualBasic
Assembly:  Microsoft.VisualBasic (in Microsoft.VisualBasic.dll)

static member InStr : 
        Start:int * 
        String1:string * 
        String2:string * 
        Compare:CompareMethod -> int

Parameters

Start
Type: System.Int32

Optional. Numeric expression that sets the starting position for each search. If omitted, search begins at the first character position. The start index is 1-based.

String1
Type: System.String

Required. String expression being searched.

String2
Type: System.String

Required. String expression sought.

Compare
Type: Microsoft.VisualBasic.CompareMethod

Optional. Specifies the type of string comparison. If Compare is omitted, the Option Compare setting determines the type of comparison.

Return Value

Type: System.Int32

If

InStr returns

String1 is zero length or Nothing

0

String2 is zero length or Nothing

start

String2 is not found

0

String2 is found within String1

Position where match begins

Start > length of String1

0

ExceptionCondition
ArgumentException

Start < 1.

Typically, the InStr function is used when parsing strings.

NoteNote

The InStrB function in previous versions of Visual Basic returns a number of bytes rather than a character position. It is used primarily for converting strings in double-byte character set (DBCS) applications. All Visual Basic 2005 strings are in Unicode, and InStrB is no longer supported.

The Compare argument settings are:

Constant

Value

Description

Binary

0

Performs a binary comparison

Text

1

Performs a text comparison

This example uses the InStr function to return the position of the first occurrence of one string within another.

' String to search in. 
Dim SearchString As String = "XXpXXpXXPXXP" 
' Search for "P". 
Dim SearchChar As String = "P" 

Dim TestPos As Integer 
' A textual comparison starting at position 4. Returns 6.
TestPos = InStr(4, SearchString, SearchChar, CompareMethod.Text)

' A binary comparison starting at position 1. Returns 9.
TestPos = InStr(1, SearchString, SearchChar, CompareMethod.Binary)

' If Option Compare is not set, or set to Binary, return 9. 
' If Option Compare is set to Text, returns 3.
TestPos = InStr(SearchString, SearchChar)

' Returns 0.
TestPos = InStr(1, SearchString, "W")

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
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