Memory Error Writing Text File

I am exporting a large dataset to a delimited file.  Unless I run the script on a system that has a ton of memory, I get a memory error.

System.OutOfMemoryException: Exception of type 'System.OutOfMemoryException' was thrown.

The file that is being created actually never gains in size (remains 0 KB) until the file is completly writting, which tells me that all of this work is being done in memory.  How can I do this so that while it is writing the file, the file actually gains size which reduces the memory overhead?  See code attached.

Dim Seperator As String
        Seperator = vbTab
        Dim linea As String
        Dim sw As StreamWriter
        Dim strBuilder As New System.Text.StringBuilder
        sw = File.CreateText("pathtofile.txt")
        Try            
            Dim objCmd As New OdbcCommand(Sql, objconn)
            Dim myAdapter As New OdbcDataAdapter(objCmd)
            Dim ds As New DataSet()     
            Try
                'Fill Dataset
                myAdapter.Fill(ds, "mln")
            Catch ex As Exception
                Console.WriteLine("Error filling dataset: " & ex.tostring)
            End Try
           
            For Each Dr As DataRow In ds.Tables(0).Rows
                strBuilder.Append("")

                strBuilder.Append(Dr(0) & Seperator) 
                strBuilder.Append(Dr(1) & Seperator) 
                strBuilder.Append(Dr(2) & Seperator) 
                strBuilder.Append(Dr(3) & Seperator) 
                ' Plus many more

                strBuilder.AppendLine()               
            Next
            linea = strBuilder.ToString
            sw.WriteLine(linea)
            strBuilder.Remove(0, strBuilder.Length)
        Catch ex As Exception
            Console.WriteLine(ex.ToString)    
        End Try

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