Articolo
11/18/2011

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

Microsoft Silverlight will reach end of support after October 2021. Learn more.

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)

Syntax

'Declaration
Public Shared Function InStr ( _
    Start As Integer, _
    String1 As String, _
    String2 As String, _
    Compare As CompareMethod _
) As Integer

public static int InStr(
    int Start,
    string String1,
    string String2,
    CompareMethod Compare
)

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 String1 is zero length or Nothing, InStr returns 0. If String2 is zero length or Nothing, InStr returns start. If String2 is not found, InStr returns 0. If String2 is found within String1, InStr returns position where match begins. If Start > String2, InStr returns 0.

Remarks

Typically, the InStr function is used when parsing strings.

The Compare argument settings are:

Constant	Value	Description
Binary	0	Performs a binary comparison
Text	1	Performs a text comparison

Examples

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")

Version Information

Silverlight

Supported in: 5, 4, 3

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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