Imports System

Imports System.Data

Imports System.Data.DataSetExtensions

Imports System.Linq

​

Public Module Module1

    Public Sub Main()

        dim dt as new DataTable

        dim dc as new DataColumn

        dc.DataType = System.Type.GetType("System.String")

        dc.ColumnName = "Coluna X"

        dt.Columns.Add(dc)

        For Each str As String In {"123451", "154321", "134561"}

            dim dr as DataRow

            dr = dt.NewRow()

            dr("Coluna X") = str

            dt.Rows.Add(dr) 

        Next

​

        dim dt2 as DataTable = dt.Copy

        'replace the first character in a loop

        For Each dr As DataRow In dt.Rows

            dr("Coluna X") = "Y" + dr("Coluna X").ToString().Substring(1)

        Next

​

        'use linq to replace the first character

        dt2.AsEnumerable.ToList.ForEach(sub(a) a.SetField("Coluna X", "Y" + a.Field(Of String)("Coluna X").ToString().Substring(1)))

        Console.WriteLine("Items inside datatable: " + String.join(", ", dt.AsEnumerable().Select(Function(a) a.Field(Of String)("Coluna X"))))

        Console.WriteLine("Items inside datatable2: " + String.join(", ", dt2.AsEnumerable().Select(Function(a) a.Field(Of String)("Coluna X"))))

    End Sub

End Module