How can I search an array in VB.NET? - vb.net

Question

I want to be able to effectively search an array for the contents of a string.
Example:
dim arr() as string={"ravi","Kumar","Ravi","Ramesh"}
I pass the value is "ra" and I want it to return the index of 2 and 3.
How can I do this in VB.NET?

Answer 1

It's not exactly clear how you want to search the array. Here are some alternatives:
Find all items containing the exact string "Ra" (returns items 2 and 3):
Dim result As String() = Array.FindAll(arr, Function(s) s.Contains("Ra"))
Find all items starting with the exact string "Ra" (returns items 2 and 3):
Dim result As String() = Array.FindAll(arr, Function(s) s.StartsWith("Ra"))
Find all items containing any case version of "ra" (returns items 0, 2 and 3):
Dim result As String() = Array.FindAll(arr, Function(s) s.ToLower().Contains("ra"))
Find all items starting with any case version of "ra" (retuns items 0, 2 and 3):
Dim result As String() = Array.FindAll(arr, Function(s) s.ToLower().StartsWith("ra"))
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If you are not using VB 9+ then you don't have anonymous functions, so you have to create a named function.
Example:
Function ContainsRa(s As String) As Boolean
Return s.Contains("Ra")
End Function
Usage:
Dim result As String() = Array.FindAll(arr, ContainsRa)
Having a function that only can compare to a specific string isn't always very useful, so to be able to specify a string to compare to you would have to put it in a class to have somewhere to store the string:
Public Class ArrayComparer
Private _compareTo As String
Public Sub New(compareTo As String)
_compareTo = compareTo
End Sub
Function Contains(s As String) As Boolean
Return s.Contains(_compareTo)
End Function
Function StartsWith(s As String) As Boolean
Return s.StartsWith(_compareTo)
End Function
End Class
Usage:
Dim result As String() = Array.FindAll(arr, New ArrayComparer("Ra").Contains)

Answer 2

Dim inputString As String = "ra"
Enumerable.Range(0, arr.Length).Where(Function(x) arr(x).ToLower().Contains(inputString.ToLower()))

Answer 3

If you want an efficient search that is often repeated, first sort the array (Array.Sort) and then use Array.BinarySearch.

Answer 4

In case you were looking for an older version of .NET then use:
Module Module1
Sub Main()
Dim arr() As String = {"ravi", "Kumar", "Ravi", "Ramesh"}
Dim result As New List(Of Integer)
For i As Integer = 0 To arr.Length
If arr(i).Contains("ra") Then result.Add(i)
Next
End Sub
End Module

Answer 5

check this..
string[] strArray = { "ABC", "BCD", "CDE", "DEF", "EFG", "FGH", "GHI" };
Array.IndexOf(strArray, "C"); // not found, returns -1
Array.IndexOf(strArray, "CDE"); // found, returns index

Answer 6

compare properties in the array if one matches the input then set something to the value of the loops current position, which is also the index of the current looked up item.
simple eg.
dim x,y,z as integer
dim aNames, aIndexes as array
dim sFind as string
for x = 1 to length(aNames)
if aNames(x) = sFind then y = x
y is then the index of the item in the array, then loop could be used to store these in an array also so instead of the above you would have:
z = 1
for x = 1 to length(aNames)
if aNames(x) = sFind then
aIndexes(z) = x
z = z + 1
endif

Answer 7

VB
Dim arr() As String = {"ravi", "Kumar", "Ravi", "Ramesh"}
Dim result = arr.Where(Function(a) a.Contains("ra")).Select(Function(s) Array.IndexOf(arr, s)).ToArray()
C#
string[] arr = { "ravi", "Kumar", "Ravi", "Ramesh" };
var result = arr.Where(a => a.Contains("Ra")).Select(a => Array.IndexOf(arr, a)).ToArray();
-----Detailed------
Module Module1
Sub Main()
Dim arr() As String = {"ravi", "Kumar", "Ravi", "Ramesh"}
Dim searchStr = "ra"
'Not case sensitive - checks if item starts with searchStr
Dim result1 = arr.Where(Function(a) a.ToLower.StartsWith(searchStr)).Select(Function(s) Array.IndexOf(arr, s)).ToArray
'Case sensitive - checks if item starts with searchStr
Dim result2 = arr.Where(Function(a) a.StartsWith(searchStr)).Select(Function(s) Array.IndexOf(arr, s)).ToArray
'Not case sensitive - checks if item contains searchStr
Dim result3 = arr.Where(Function(a) a.ToLower.Contains(searchStr)).Select(Function(s) Array.IndexOf(arr, s)).ToArray
Stop
End Sub
End Module

Answer 8

Never use .ToLower and .ToUpper.
I just had problems in Turkey where there are 4 "i" letters. When using ToUpper I got the wrong "Ì" one and it fails.
Use invariant string comparisons:
Const LNK as String = "LINK"
Dim myString = "Link"
Bad:
If myString.ToUpper = LNK Then...
Good and works in the entire world:
If String.Equals(myString, LNK , StringComparison.InvariantCultureIgnoreCase) Then...

Answer 9

This would do the trick, returning the values at indeces 0, 2 and 3.
Array.FindAll(arr, Function(s) s.ToLower().StartsWith("ra"))