vb.net中using的简单介绍

VB.NET引用

Private Function ReadFile(ByRef a As String) As String

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a = "bian"

End Function

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

Dim a As String = "yuanlai"

ReadFile(a)

''想要的结果就是在这里使用a的值是"bian"

MsgBox(a)

End Sub

===================

以上就可以,不知道你“ByRef a As b”的b是什么东西

vb.net退出这个form窗口怎么同时取消对图片的占用?

只需要用变量存储 Image 对象,然后不需要的时候释放掉就行了。

Dim img1 As Image

img1 = Image.FromFile(pic)

PictureBox1.Image = img1

'窗口关闭时

img1 = Nothing

如满意,请采纳。

vb.net使用打开对话框,打开一个文本文件显示在文本框中,然后对文本框中的信息进行编辑后

读文件内容到TextBox :

Try

Using sr As StreamReader = New StreamReader("C:\\TestFile.txt")

textbox1.Text = sr.ReadToEnd()

End Using

Catch E As Exception

Console.WriteLine(E.Message)

End Try

修改完成后,保存到文件:

Using sw As StreamWriter = New StreamWriter("C:\\TestFile.txt")

sw.Write(textbox1.Text)

sw.Close()

End Using

其中,流构造的参数

New StreamReader("C:\\TestFile.txt")

New StreamWriter("C:\\TestFile.txt")

中的"C:\\TestFile.txt"可以用OpenFileDialog和SaveFileDialog的FileName属性替换.

Dim openFileDialog1 As New OpenFileDialog()

openFileDialog1.InitialDirectory = "c:\"

openFileDialog1.Filter = "txt files (*.txt)|*.txt|All files (*.*)|*.*"

openFileDialog1.FilterIndex = 2

openFileDialog1.RestoreDirectory = True

If openFileDialog1.ShowDialog() = System.Windows.Forms.DialogResult.OK Then

Try

Using sr As StreamReader = New StreamReader(openFileDialog1.FileName)

textbox1.Text = sr.ReadToEnd()

End Using

Catch E As Exception

Console.WriteLine(E.Message)

End Try

End If

保存的时候换成SaveFileDialog就好

VB.NET备份SQL数据库

using System;

using System.Data;

using System.Configuration;

using System.Collections;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Web.UI.HtmlControls;

using System.IO;

using System.Text;

using _5dRss.Const;

using _5dRss.lib.Data.Tool;

public partial class admin_admin_dbmanage : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{

//生成备份文件列表

ListBackupFiles();

if (!Page.IsPostBack)

{

Showmsg.Visible = false;

//数据库路径

lilDBPath.Text = HttpContext.Current.Request.PhysicalApplicationPath + "App_Data\\" + ConfigurationSettings.AppSettings["DBFile"];

//新建一个 FileInfo 对象,并获得数据库文件的大小,然后转换单位为KB

FileInfo myFileInfo = new FileInfo(lilDBPath.Text);

lilDBSize.Text = Convert.ToString(myFileInfo.Length/1024) + " KB";

//如果两个参数都不为空,则继续执行

if (Request.QueryString["cmd"] != null Request.QueryString["source"] != null)

{

//备份数据库原文件名

string sourceFileName = Request.QueryString["source"];

//如果 cmd 参数为 DelFile

if (Request.QueryString["cmd"].Equals("DelFile"))

{

//删除备份数据库文件

File.Delete(HttpContext.Current.Request.PhysicalApplicationPath + "Backup\\" + sourceFileName);

//刷新备份文件列表

ListBackupFiles();

Showmsg.Visible = true;

Showmsg.Text = "div align='center' style='margin-bottom:8px;'img src='images/aL.gif' style='margin-bottom:-6px;'/span class='alertTxt'删除备份数据库成功!/spanimg src='images/aR.gif' style='margin-bottom:-6px;'//div";

}

//如果 cmd 参数为 Restore

if (Request.QueryString["cmd"].Equals("Restore"))

{

//用备份文件覆盖原文件

File.Copy(HttpContext.Current.Request.PhysicalApplicationPath + "Backup\\" + sourceFileName, HttpContext.Current.Request.PhysicalApplicationPath + "App_Data\\" + ConfigurationSettings.AppSettings["DBFile"], true);

//刷新备份文件列表

ListBackupFiles();

Showmsg.Visible = true;

Showmsg.Text = "div align='center' style='margin-bottom:8px;'img src='images/aL.gif' style='margin-bottom:-6px;'/span class='alertTxt'还原备份数据库成功!/spanimg src='images/aR.gif' style='margin-bottom:-6px;'//div";

}

}

}

}

protected void lnkbtnCompactDB_Click(object sender, EventArgs e)

{

//压缩修复数据库

AccessDBtool.CompactAccessDB(SysConfig.ConnectionString, HttpContext.Current.Request.PhysicalApplicationPath + "App_Data\\" + ConfigurationSettings.AppSettings["DBFile"]);

Showmsg.Visible = true;

Showmsg.Text = "div align='center' style='margin-bottom:8px;'img src='images/aL.gif' style='margin-bottom:-6px;'/span class='alertTxt'压缩修复数据库成功!/spanimg src='images/aR.gif' style='margin-bottom:-6px;'//div";

}

protected void lnkbtnBackupDB_Click(object sender, EventArgs e)

{

string sourceFileName = HttpContext.Current.Request.PhysicalApplicationPath + "App_Data\\" + ConfigurationSettings.AppSettings["DBFile"];

string destFileName = HttpContext.Current.Request.PhysicalApplicationPath + "Backup\\" + "Backup_";

destFileName += DateTime.Now.ToString("yyyyMMddHHmmss");

destFileName += ".mbk";

//将数据库文件Copy到Backup目录,如果有重名文件就覆盖原文件

File.Copy(sourceFileName, destFileName, true);

//生成备份文件列表

ListBackupFiles();

Showmsg.Visible = true;

Showmsg.Text = "div align='center' style='margin-bottom:8px;'img src='images/aL.gif' style='margin-bottom:-6px;'/span class='alertTxt'备份数据库成功!/spanimg src='images/aR.gif' style='margin-bottom:-6px;'//div";

}

/// summary

/// 生成备份文件列表

/// /summary

/// returns文件列表,文件详细信息及操作选项的HTML代码/returns

public void ListBackupFiles()

{

//如果目录不存在则创建次目录

if (!Directory.Exists(HttpContext.Current.Request.PhysicalApplicationPath + "Backup\\"))

Directory.CreateDirectory(HttpContext.Current.Request.PhysicalApplicationPath + "Backup\\");

DirectoryInfo mydir = new DirectoryInfo(HttpContext.Current.Request.PhysicalApplicationPath + "Backup\\");

StringBuilder sb = new StringBuilder();

foreach (FileInfo f in mydir.GetFiles())

{

sb.Append("a href='backup/" + f.Name + "' target='_blank'img border='0' src='images/mdb.gif' style='margin:4px 3px -3px 0px'/" + f.Name + "/a a href='?cmd=DelFilesource=" + f.Name + "' title='删除备份文件'删除/a | a href='?cmd=Restoresource=" + f.Name + "' title='删除备份文件'还原数据库/a | " + f.Length/1024 + " KB | " + f.CreationTime + "br /");

}

lilBackupFileList.Text = sb.ToString();

}

}

把下面这句换成你的数据库地址:

//数据库路径

// lilDBPath.Text = HttpContext.Current.Request.PhysicalApplicationPath + "App_Data\\" + ConfigurationSettings.AppSettings["DBFile"];

VB.NET存取注册表项的几个函数

1、首先引用命名空间:using Microsoft.Win32; 

2、几个基本主键:

Registry.ClassesRoot;对应于HKEY_CLASSES_ROOT主键

Registry.CurrentUser;   对应于HKEY_CURRENT_USER主键

Registry.LocalMachine;   对应于 HKEY_LOCAL_MACHINE主键

Registry.User;   对应于 HKEY_USER主键

Registry.CurrentConfig;   对应于HEKY_CURRENT_CONFIG主键

Registry.DynDa; 对应于HKEY_DYN_DATA主键

Registry.PerformanceData; 对应于HKEY_PERFORMANCE_DATA主键

3、返回或创建一个注册表键

Dim Key1 As Microsoft.Win32.RegistryKey

Key1 = My.Computer.Registry.CurrentUser   '返回当前用户键

Dim Key2 As Microsoft.Win32.RegistryKey

Key2 = Key1.OpenSubKey("northsnow")       '返回当前用户键下的northsnow键

If Key2 Is Nothing Then

Key2 = Key1.CreateSubKey("northsnow")  '如果键不存在就创建它

End If

如何在vb.net中使用vb6中api的功能,用.netFrameworkme么?

不知道你想实现什么功能。

如果你的意思是使用某种WINDOW API相对应的功能。需要查看MSDN中

.NETFRAMEWORK是否有相关的类库与函数。

VB中Declare 用于在模块级别中声明对动态链接库 (DLL) 中外部过程的引用。

可以引用windows api的函数。

但是如果你需要寻找一些你需要的类似WINDOWSAPI功能的函数。例如:FindWindow. 有一些函数功能类似。

例如 :Process currentProcess = Process.GetCurrentProcess();

IntPtr hWndToProcess = currentProcess .MainWindowHandle;

获得程序进程的窗口。

但是要是获得桌面窗口这个就要用到api了。


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