DLL:

背景：

开始做中谷项目时我还不知道怎么用DLL。后来看别人用才试着去学习使用。虽然现在已经会用了，但DLL的强大之处我了解的还远远不够。下面先简单说下DLL。

DLL是神马？

Windows操作系统是非常依赖于动态链接库（DLL）中的函数和数据的，实际上操作系统中几乎所有的内容都由DLL以一种或另外一种形式代表着，例如显示的字体和图标存储在GDI DLL中、显示windows桌面和处理用户的输入所需要的代码被存储在一个User DLL中、Windows编程所需要的大量API函数也呗包含在Kernel DLL中。

使用DLL优点多多：

最主要的一点是多个应用程序、甚至不同语言编写的应用程序可以共享一个DLL文件，实现资源“共享”，这样就大大缩小了应用程序的执行代码，有效利用内存；另一个优点是DLL文件作为一个单独的程序模块，封装性、独立性好，在软件需要升级的时候，开发人员只需要修改相应的DLl文件就可以了，而且，当DLL中的函数改变后，只要不是参数的改变，程序代码并不需要重新编译，这在编程时大大提高了软件开发和维护的效率。

我要使用啦：

打印：

很多窗体都需要打印功能，为了调用方便，我把打印写成一个类封装成DLL，然后在程序里添加引用。Print类代码也附到这里，不是重点。

Imports System.Drawing
Imports System.Drawing.Printing
Imports System.Windows.Forms

Public Class Class1

    Private PrintFont As New Font("宋体", 10)
    Private PrintLines As Integer = 50
    Private PrintRecordNumber As Integer = 45
    Private DataGridSource As DataGridView

    Private ev As PrintPageEventArgs
    Private PrintDataGrid As PrintDocument
    Private PrintPriview As PrintPreviewDialog
    Private PageSetup As PageSetupDialog
    Private PrintScale As Double = 1
    Private DataGridColumn As DataColumn
    Private DataGridRow As DataRow
    Private DataGridTable As DataTable
    Private Cols As Integer
    Private Rows As Integer = 1
    Private ColsCount As Integer
    Private PrintingLineNumber As Integer = 0
    Private PageRecordNumber As Integer
    Dim X_unit As Integer
    Dim Y_unit As Integer
    Dim _strPrint As String
    Private PrintingPageNumber As Integer = 0
    Private PageNumber As Integer
    Private PrintRecordLeave As Integer
    Private PrintRecordComplete As Integer = 0

    ''' 

    ''' 设置打印字体
    ''' 
    ''' 
  
    ''' 
  
    Public WriteOnly Property setPrintFont() As System.Drawing.Font
        Set(ByVal Value As System.Drawing.Font)
            PrintFont = Value
        End Set
    End Property


    Public WriteOnly Property setPrintRecordNumber() As Integer
        Set(ByVal Value As Integer)
            PrintRecordNumber = Value
        End Set
    End Property

    ''' 

    ''' 设置表头
    ''' 
    ''' 
  
    ''' 
  
    ''' 
  
    Public Property setstrPrint() As String
        Set(ByVal value As String)
            _strPrint = value
        End Set
        Get
            Return _strPrint
        End Get
    End Property

    Sub New(ByVal TableSource As DataGridView)
        DataGridSource = TableSource
        DataGridTable = New DataTable
        DataGridTable = DataGridSource.DataSource()
        ColsCount = DataGridTable.Columns.Count
    End Sub

    Public Sub Print()
        Try
            PrintDataGrid = New System.Drawing.Printing.PrintDocument
            AddHandler PrintDataGrid.PrintPage, AddressOf Me.PrintDataGrid_PrintPage
            '* 
            PageSetup = New PageSetupDialog
            PageSetup.PageSettings = PrintDataGrid.DefaultPageSettings
            If PageSetup.ShowDialog() = DialogResult.Cancel Then
                Exit Sub
            End If
            '* 
            If PrintDataGrid.DefaultPageSettings.Landscape = False Then
                PrintLines = PrintDataGrid.DefaultPageSettings.PaperSize.Height / (PrintFont.Height + 5)
            Else
                PrintLines = PrintDataGrid.DefaultPageSettings.PaperSize.Width / (PrintFont.Height + 5)
            End If
            '* 
            If PrintDataGrid.DefaultPageSettings.PaperSize.PaperName.ToString = "custom" Then

            End If
            '* 
            PrintPriview = New PrintPreviewDialog
            PrintPriview.Document = PrintDataGrid
            PrintPriview.ShowDialog()

        Catch ex As Exception
            MessageBox.Show("错误:" & ex.ToString)
        End Try
    End Sub

    Private Sub PrintDataGrid_PrintPage(ByVal sender As Object, ByVal ev As System.Drawing.Printing.PrintPageEventArgs)
        Dim strPrint As String = Nothing
        Dim DrawBrush As New SolidBrush(System.Drawing.Color.Blue)
        Dim X As In