HOW TO FIND OCCURRENCE OF A LETTER IN A STRING IN VB.NET

HOW TO FIND OCCURRENCE OF A LETTER IN A STRING IN VB.NET
first and last occurrence of the letter A in a string
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Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Dim s As String = "HAI Mr ANURAJ S "
Dim x As Integer
x = s.IndexOf("A")'first occurrence of the letter A in a string
Dim k As Integer = s.LastIndexOf("A")'LAST occurrence of the letter A in a string
MsgBox(x)
MsgBox(k)
End Sub
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find all occurrence of the letter A in a string
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Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim s As String = "HAI Mr ANURAJ S"
Dim x As Integer
Dim y As Integer
Do
x = s.IndexOf("A", x)
MessageBox.Show(x)
x += 1
y = s.IndexOf("A", x)
Loop Until y = -1
End Sub
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