在vb.net中提取子字符串

Question

I have following string, and would need to extract the X and Y values cut to a single digit after the point.

A234X78.027Y141.864D1234.2

There are a few variables that can change here:

• the string can have any length and contain any number of values
• I know that X and Y are Always present, but they do not have to be in a specific order in the string
• Each value for X or Y can have any lenght.. for example x can be 1.1 or 1234.1
• it is not imperative that X or Y do have a point. it can also be a round number, for example X78Y141.34561 (note that X has no point) If there is no point I am ok with the value, but if there is a point then I would need the first digit after the point. (rounded)

As a Result of the above string I would need two string variables containing the values 78.0 and 141.9

EDIT: Updated the last sentence, the variables should contain JUST the value, no X and Y. Sorry for the mistake

Update, code as requested

---

        Dim objReader As New System.IO.StreamReader(FILE_NAME)

        Do While objReader.Peek() <> -1
            Dim curline As String = objReader.ReadLine()  'curline = G1X39.594Y234.826F1800.0
            If curline.Contains("X") Then
                Dim t As String = ExtractPoint(curline, "X"c) 't = "39.594"
                Dim d As Double = Math.Round(Convert.ToDouble(t), 1) 'd= 39594.0
                destx = d * 10 'destx = 395940

            End If
         Loop

---

Function ExtractPoint(dataString As String, character As Char) As String
    Dim substring As String = String.Empty

    Dim xIndex As Integer = dataString.IndexOf(character) + 1
    substring += dataString(xIndex)
    xIndex = xIndex + 1
    While (xIndex < dataString.Length AndAlso Char.IsLetter(dataString(xIndex)) = False)
        substring += dataString(xIndex)
        xIndex = xIndex + 1
    End While

    Return substring
End Function

Answer 1

Have you looked into Regular Expressions?

    Dim x As System.Text.RegularExpressions.Match = System.Text.RegularExpressions.Regex.Match(TextBox1.Text, "X\d+([.]\d{1})?")
    Dim y As System.Text.RegularExpressions.Match = System.Text.RegularExpressions.Regex.Match(TextBox1.Text, "Y\d+([.]\d{1})?")

    MsgBox(x.ToString & " -- " & y.ToString)

I believe this will do what you are looking for if I understood correctly.

EDIT For Only getting the numbers after X and Y

Based off my original code, you could do something like this. This also rounds the numbers to the nearest one decimal place.

    Dim x As System.Text.RegularExpressions.Match = System.Text.RegularExpressions.Regex.Match(TextBox1.Text, "X(\d+([.]\d{2})?)")
    Dim y As System.Text.RegularExpressions.Match = System.Text.RegularExpressions.Regex.Match(TextBox1.Text, "Y(\d+([.]\d{2})?)")

    MsgBox(Math.Round(CDbl(x.Groups(1).Value), 1) & " -- " & Math.Round(CDbl(y.Groups(1).Value), 1))

Updated code for added code

    Dim s As String = "A234X78.027Y141.864D1234.2"
    Dim dX As Double = Extract(s, "X")
    Dim dY As Double = Extract(s, "Y")
    MsgBox(dX * 10 & "-" & dY * 10)

    Private Function Extract(ByRef a As String, ByRef l As String) As Double
        Dim x As System.Text.RegularExpressions.Match = System.Text.RegularExpressions.Regex.Match(a, l & "(\d+([.]\d{2})?)")
        Return Math.Round(CDbl(x.Groups(1).Value), 1)
    End Function

Answer 2

Your sample data indicates that fields are separated by letters, and the last letter ends with the string. Knowing that you can parse your desired letters out manually and round to 1 decimal point.

This also takes into account when there is no decimal point, but it will display a .0 at the end of the number.

EDIT

Moved common code to a function

Update

Doesn't include the letter as part of the output

Sub Main()
    Dim dataString As String = "G1X39.594Y234.826F1800.0"

    Dim xString As String = ExtractPoint(dataString, "X"c)
    Dim yString As String = ExtractPoint(dataString, "Y"c)

    Dim xDouble As Double = Math.Round(Convert.ToDouble(xString), 1)
    Dim yDouble As Double = Math.Round(Convert.ToDouble(yString), 1)

    Console.WriteLine(xDouble.ToString("F1"))
    Console.WriteLine(yDouble.ToString("F1"))

    Console.WriteLine((xDouble * 10).ToString("F1"))
    Console.WriteLine((yDouble * 10).ToString("F1"))

    Console.ReadLine()
End Sub

Function ExtractPoint(dataString As String, character As Char) As String
    Dim substring As String = String.Empty

    Dim xIndex As Integer = dataString.IndexOf(character) + 1
    substring += dataString(xIndex)
    xIndex = xIndex + 1
    While (xIndex < dataString.Length AndAlso Char.IsLetter(dataString(xIndex)) = False)
        substring += dataString(xIndex)
        xIndex = xIndex + 1
    End While

    Return substring
End Function

Results:

Answer 3

Here is a simple LINQ function that should do it for you (no regex, no long code):

Private Function ExtractX(s As String, symbol As Char) As String
    Dim XPos = s.IndexOf(symbol)
    Dim s1 = s.Substring(XPos + 1).TakeWhile(Function(c) Char.IsDigit(c)).ToArray()
    If (XPos + 1 + s1.Length < s.Length) AndAlso s.Substring(XPos + 1 + s1.Length)(0) = "."c AndAlso Char.IsDigit(s.Substring(XPos + 1 + s1.Length)(1)) Then
      Return String.Join("", s1, s.Substring(XPos + 1 + s1.Length, 2))
    Else
      Return s1
    End If
End Function

Call it like this:

Dim s = "A234X78.027Y141.864D1234.2"
Dim x = ExtractX(s, "X"c)
Dim y = ExtractX(s, "Y"c)