FUNCTIONS in Programming

Functions returns a value/statement/datatable,etc when it is being triggered. This is a sample of function that returns a datatable :

    Public Function Get_records() As Data.DataTable
        Try
            Dim sSQL As String = "SELECT * FROM tenant_management.tbluser WHERE active = 'Y'"

            Dim myDA As New MySqlDataAdapter(sSQL, myCon)
            Dim dsData As New DataSet()

            myDA.Fill(dsData, "Data")

            Return dsData.Tables("Data")

            myCon.Close()
        Catch ex As Exception
            myCon.Close()
            Throw
        Finally
            myCon.Close()
        End Try
    End Function

This can be used in a class or in your winform. 

"mycon" in this function is my connection which should be assigned a connectionstring. 

http://connectionstrings.com/

To call this function, you should assign your grid's datasource property to this function which returns a datatable. 

If you are using a  class, the syntax of assigning the datasource should be like this:

        Dim getClass As New Classname()
        grd.DataSource = getClass.Get_records

if you are not using a class and you just use the function in the winform, the syntax should be like this:

        datagrid.DataSource = Get_records

The bottomline is: you can use your function anytime you want. You just simply call the function instead of coding again the whole content of the function.