vbnewbie vbnewbie - 1 year ago 103
Vb.net Question

How to return a string from a text file with condition met?

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Public Sub openDB()
Dim Lines As New List(Of String)

' Open the file using a stream reader.
Using sr As New StreamReader("Config.txt")
Dim line As String
' Read the stream to a string and write the string to the console.
line = sr.ReadLine()
Do Until String.IsNullOrEmpty(line)
line = sr.ReadLine
End Using
Catch e As Exception
Console.WriteLine("The file could not be read:")
End Try

Dim dbname As String = g_DatabaseName
Dim server As String = Lines.Where(Function(str) str.Contains("server =")).ToString
Dim user As String = ""
Dim password As String = ""

conn = New MySqlConnection
conn.ConnectionString = String.Format("server={0}; user id={1}; password={2}; database={3}; pooling=false; Convert Zero Datetime=True", server, user, password, dbname)
End Sub

Im try to return some string from a text file, so I use StreamReader to read the file and store them into a list. Now I try to declare a variable to get "localhost" from list of string, but the code below is not work for me.

Dim server As String = Lines.Where(Function(str) str.Contains("server

Answer Source

Enumerable.Where does not return a single string but possibly multiple, using ToString gives you not the first matching line but just the name of the type which is System.Linq.Enumerable+WhereArrayIterator1[System.String].

Either declare it as IEnumerable(Of String) or use First/ FirstOrDefault to get the first line that matches the condition:

Dim serverLine As String = Lines
    .Where(Function(str) str.Contains("server ="))

You can also use the overload of FirstOrDefault(Nothing if there was no such line):

Dim serverLine As String = Lines.FirstOrDefault(Function(str) str.Contains("server ="))

To extract Localhost:

Dim server As String = serverLine.Substring(serverLine.IndexOf("server =") + "server =".Length).Trim(""""c, " "c)
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