Finding Substring of String VB - vb.net

Question

1.The Following Program will get two inputs from user i.e A & B
2. Than Find the sub string from B.
3. Finally Print the result.
While my code is
Dim a As String
Dim b As String
a = InputBox("Enter First String", a)
b = InputBox("Enter 2nd String", b)
Dim i As Integer
Dim j As Integer = 0
Dim k As Integer = 0
Dim substr As Integer = 0
For i = 0 To a.Length - 1
If a(i) = b(j) Then
j += 1
If b(j) = 0 Then
MsgBox("second string is substring of first one")
substr = 1
Exit For
End If
End If
Next i
For i = 0 To b.Length - 1
If b(i) = a(k) Then
k += 1
If a(k) = 0 Then
MsgBox(" first string is substring of second string")
substr = 1
Exit For
End If
End If
Next i
If substr = 0 Then
MsgBox("no substring present")
End If
End Sub
While compiling it gives following debugging errors.
Line Col
Error 1 Operator '=' is not defined for types 'Char' and 'Integer'. 17 24
Error 2 Operator '=' is not defined for types 'Char' and 'Integer'. 27 24

Answer 1

It is because of these lines:
If b(j) = 0 Then
If a(k) = 0 Then
As a(k) and b(j) are both of the Char data type (think of the string as an array of characters) but you are trying to compare them to an int (0).
If you are looking for a substring and you're using VB.NET you could try using the IndexOf method, for a very naive example:
If a.IndexOf(b) > -1 Then
MsgBox("b is a substring of a")
ElseIf b.IndexOf(a) > -1 Then
MsgBox("a is a substring of b")
Else
MsgBox("No substring found")
End
If you are using VBA, you could also use InStr but I think with this the string is 1-indexed instead of 0-indexed (as they are in VB.NET) so your check may look something like:
If InStr(a,b) > 0 Then
MsgBox("b is a substring of a")
ElseIf InStr(b,a) > 0 Then
MsgBox("a is a substring of b")
Else
MsgBox("No substring found")
End