vb.net 連接SQL數(shù)據(jù)庫(kù)登錄代碼

問(wèn)題應(yīng)該出在你的查詢語(yǔ)句的結(jié)果沒(méi)有值,你用你的查詢語(yǔ)句到SQL中是否有返回值?記得加上你的條件,另外,你語(yǔ)句里這一句是多余的.Dim s As Object = sComm.ExecuteScalar 以下語(yǔ)句測(cè)試正常 Dim myCn As New SqlClient.SqlConnection Try myCn.ConnectionString = sConnString myCn.Open() Dim mySQL As String = "SELECT * FROM ygzl" Dim sComm As New SqlClient.SqlCommand(mySQL, myCn) If sComm.ExecuteScalar Then Dim User_MainForm As New Form1 User_MainForm.Show() Else MsgBox("用戶名或密碼不正確，請(qǐng)重試！") End If Catch ex As Exception MsgBox(ex.Message) Finally myCn.Close() '關(guān)閉連接 End Try

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求VB.NET2010操作ACCESS數(shù)據(jù)庫(kù)的完整代碼

Imports System.Data.OleDb

Public Class Parking

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

Now_Timer.Enabled = True

End Sub

Private Sub Now_Timer_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Now_Timer.Tick

Now_Time_Label.Text = "當(dāng)前時(shí)間：" Date.Now

End Sub

Private Sub Enter_Button_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Enter_Button.Click

'定義一個(gè)OLEDB連接字符串

Dim conStr As String = "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=F:\test\test.mdb"

'實(shí)例化OLEDB連接

Dim con As OleDbConnection = New OleDbConnection(conStr)

Dim sql As New System.Text.StringBuilder

'定義數(shù)據(jù)庫(kù)插入語(yǔ)句

sql.Append("insert into Time_billing([Car_Num],[Enter_Time])")

sql.Append("values('" Trim(Car_Num_Text.Text) "','" Date.Now "')")

'打開(kāi)數(shù)據(jù)庫(kù)鏈接

con.Open()

'定義執(zhí)行命令

Dim cmd As New System.Data.OleDb.OleDbCommand(sql.ToString, con)

'執(zhí)行命令

cmd.ExecuteNonQuery()

'關(guān)閉數(shù)據(jù)庫(kù)鏈接

con.Close()

MsgBox("提交成功！")

End Sub

Private Sub Leave_Button_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Leave_Button.Click

Dim Time_Length As Double

Dim Pack_Fee As Double

Dim Enter_time As Date

Dim Leave_time As Date

Dim conStr As String = "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=F:\test\test.mdb"

Dim con As OleDbConnection = New OleDbConnection(conStr)

Dim selSql As New System.Text.StringBuilder

Dim inSql As New System.Text.StringBuilder

Dim upSql As New System.Text.StringBuilder

Dim delSql As New System.Text.StringBuilder

Dim dr As OleDbDataReader

con.Open()

'SQL拼接過(guò)程中最后不需要有分號(hào)

'在賦值時(shí)，讀取字段值時(shí)必須使用在數(shù)據(jù)庫(kù)客戶端查詢時(shí)顯示的字段名

selSql.Append("select")

selSql.Append(" Enter_Time")

selSql.Append(" from [Time_billing]")

selSql.Append("where Car_Num = '").Append(Trim(Car_Num_Text.Text)).Append("'")

Dim selcmd As New OleDb.OleDbCommand(selSql.ToString, con)

dr = selcmd.ExecuteReader()

If dr.Read() Then

Enter_time = dr("Enter_Time")

Leave_time = Date.Now

Else

MsgBox("木有數(shù)據(jù)！")

End If

Enter_Time_Text.Text = Enter_time

Leave_Time_Text.Text = Leave_time

'求時(shí)間差

Time_Length = Math.Round(DateDiff(DateInterval.Minute, Enter_time, Leave_time) / 60, 2)

Pack_Fee = Time_Length * 5

Pack_Fee_Text.Text = Pack_Fee

inSql.Append("update [Time_billing]")

inSql.Append(" set [Leave_Time] = '").Append(Trim(Leave_Time_Text.Text)).Append("'")

inSql.Append(" ,[Packing_Fee] = '").Append(Pack_Fee).Append("'")

inSql.Append("where Car_Num = '").Append(Trim(Car_Num_Text.Text)).Append("'")

Dim incom As New OleDb.OleDbCommand(inSql.ToString, con)

incom.ExecuteNonQuery()

'con.Close()

MsgBox("結(jié)算完成！")

'con.Open()

upSql.Append("insert into Time_billing_History([Car_Num],[Enter_Time],[Leave_Time],[Packing_Fee])")

upSql.Append(" select")

upSql.Append(" [Car_Num]")

upSql.Append(",[Enter_Time]")

upSql.Append(",[Leave_Time]")

upSql.Append(",[Packing_Fee]")

upSql.Append(" from [Time_billing]")

upSql.Append("where [Car_Num] = '").Append(Trim(Car_Num_Text.Text)).Append("'")

Dim upcom As New OleDb.OleDbCommand(upSql.ToString, con)

upcom.ExecuteNonQuery()

delSql.Append("delete")

delSql.Append(" from")

delSql.Append(" [Time_billing]")

delSql.Append(" where [Car_Num] = '").Append(Trim(Car_Num_Text.Text)).Append("'")

Dim delcom As New OleDb.OleDbCommand(delSql.ToString, con)

delcom.ExecuteNonQuery()

con.Close()

End Sub

Private Sub Clear_Button_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Clear_Button.Click

Car_Num_Text.Clear()

Enter_Time_Text.Clear()

Leave_Time_Text.Clear()

Pack_Fee_Text.Clear()

End Sub

End Class

vb.net2015連接數(shù)據(jù)庫(kù)SQL2012代碼

1、 用The SQL Server .NET Data Provider連接數(shù)據(jù)庫(kù)

The SQL Server .NET Data Provider是利用SqlConnection類來(lái)連接SQL Server7.0或更高版本的數(shù)據(jù)庫(kù)，

SqlConnection類位于名稱空間System.Data.SqlClient下。

連接代碼：

Dim sqlConnection1 As SqlClient.SqlConnection

Dim strConnect As String=”data source=服務(wù)器名;initial catalog=數(shù)據(jù)庫(kù)名;user id=sa;password=;”

sqlConnection1=New System.Data.SqlClient.SqlConnection(strConnect)

sqlConnection1.open ‘打開(kāi)數(shù)據(jù)庫(kù)

sqlConnection1.close ‘關(guān)閉連接，釋放資源

2、 用The OLE DB .NET Data Provider連接數(shù)據(jù)庫(kù)

上面已經(jīng)說(shuō)過(guò)，利用The OLE DB .NET Data Provider可以訪問(wèn)Access、Oracle和SQL Server等種數(shù)據(jù)

庫(kù)，那么，它是怎樣訪問(wèn)這些數(shù)據(jù)庫(kù)的呢？The OLE DB .NET Data Provider是通過(guò)位于名稱空間Sy

stem.Data.OleDb類庫(kù)下的OleDbConnection類來(lái)連接這三種不同類型的數(shù)據(jù)庫(kù)的。下面舉例說(shuō)明:

1)連接SQL Server數(shù)據(jù)庫(kù)

Dim oleDbConnection1 As OleDb.OleDbConnection

Dim strConnect As Sting=”P(pán)rovider=SQLOLEDB;Persist Security Info=False;Data Source=服務(wù)器名;Initial Catalog=數(shù)據(jù)庫(kù)名;User ID=sa;Password=;”

oleDbConnection1=New System.Data.OleDb.OleDbConnection(strConnect)

2)連接Access數(shù)據(jù)庫(kù)

假設(shè)要連接的Access數(shù)據(jù)庫(kù)名為“Example.mdb”，存放在d:\Data\目錄下。

Dim oleDbConnection1 As OleDb.OleDbConnection

Dim strConnect As Sting=”P(pán)rovider=Microsoft.Jet.OLEDB.4.0;Data Source=d:\Data\ Example.mdb”

oleDbConnection1= New System.Data.OleDb.OleDbConnection(strConnect)

3)連接Oracle數(shù)據(jù)庫(kù)

Dim oleDbConnection1 As OleDb.OleDbConnection

Dim strConnect As Sting=”P(pán)rovider=MSDAORA;Data Source=服務(wù)器名;User ID=用戶ID;Password=密碼;”

oleDbConnection1= New System.Data.OleDb.OleDbConnection(strConnect)

3、 用The ODBC .NET Data Provider連接數(shù)據(jù)庫(kù)

The ODBC .NET Data Provider連接數(shù)據(jù)庫(kù)是通過(guò)OdbcConnection類來(lái)實(shí)現(xiàn)的，這個(gè)類位于名稱空間

Microsoft.Data.Odbc下，而名稱空間Microsoft.Data.Odbc是封裝在Microsoft.Data.Odbc.dll文件下的。

由于篇幅有限，這里就只介紹連接Sql Server和Oracle數(shù)據(jù)庫(kù)的方法，其他數(shù)據(jù)庫(kù)的連接方法基本類

似，我就不再多講了。

1)連接Sql Server數(shù)據(jù)庫(kù)

Dim odbcDbConnetion1 As Microsoft.Data.OdbcConnection

Dim strConnect As Sting=”Driver={SQL Server};Server=服務(wù)器名;Uid=sa;pwd=;Database= 數(shù)據(jù)庫(kù)名;”

odbcDbConnetion1=New Microsoft.Data.OdbcConnection(strConnect)

2)連接Oracle數(shù)據(jù)庫(kù)

Dim odbcDbConnetion1 As Microsoft.Data.OdbcConnection

Dim strConnect As Sting=”Driver={Microsoft ODBC for Oracle};Server=服務(wù)器名;Uid=sa;pwd=;”

odbcDbConnetion1=New Microsoft.Data.OdbcConnection(strConnect)

四、總結(jié)

通過(guò)本文的介紹，讀者基本掌握了在Visual Basic.NET中用ADO.NET和ODBC.NET連接各種數(shù)據(jù)庫(kù)的方法

。以上三種驅(qū)動(dòng)針對(duì)不同的數(shù)據(jù)庫(kù)，它們的性能方面也有很大的不同：The SQL Server .NET Data Provider

的效率最高；The OLE DB .NET Data Provider的效率比較底；The ODBC .NET Data Provider的效率最慢。

使用VB.net實(shí)現(xiàn)sql數(shù)據(jù)庫(kù)的備份與恢復(fù)代碼

Private Sub Button _Click(ByVal sender As System Object ByVal e As System EventArgs) Handles Button Click 備份數(shù)據(jù)庫(kù) BACKUP DATABASE Test TO DISK= C:\Backup WITH Format Dim cn As SqlConnection Dim cm As SqlCommand cn = getDB() cm = New SqlCommand( BACKUP DATABASE JXbase TO DISK= C:\Backup WITH Format cn) cn Open() cm ExecuteNonQuery() MsgBox( 備份成功 ) cn Close()

End Sub

恢復(fù) Private Sub Button _Click(ByVal sender As System Object ByVal e As System EventArgs) Handles Button Click Dim cn As New SqlConnection Dim cn As New SqlConnection Dim mydr As SqlDataReader Dim str As String

Dim tmpConnectionString As String = Data Source=JJK;Initial Catalog=master;Integrated Security=True cn ConnectionString = tmpConnectionString cn ConnectionString = tmpConnectionString cn Open() cn Open() Dim cm As SqlCommand = New SqlCommand( select spid from master sysprocesses where dbid=db_id( JXbase ) cn) mydr = cm ExecuteReader()

Dim cm As SqlCommand = New SqlCommand() cm Connection = cn

While (mydr Read()) 殺死進(jìn)程

str = kill mydr( spid ) ToString() cm CommandText = str cm CommandType = CommandType Text Application DoEvents() cm ExecuteNonQuery() 殺進(jìn)程 End While mydr Close() cm = New SqlCommand( RESTORE DATABASE JXbase FROM DISK= C:\Backup cn) 恢復(fù)備份 cm ExecuteNonQuery() MsgBox( 恢復(fù)成功成功 ) cn Close() cn Close()

lishixinzhi/Article/program/net/201311/12901

求vb.net的源代碼，最好說(shuō)明其解決問(wèn)題，越多越好，滿意加50分。

下面這段代碼，是我用來(lái)計(jì)算每個(gè)月存500元進(jìn)銀行，連續(xù)30年，最后連本帶利能有多少錢(qián)。這里面涉及復(fù)利計(jì)算。界面中右邊的文本框用來(lái)輸出每一次計(jì)算的結(jié)果。

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

? Dim nianxian As Integer '年限變量

? Dim dingcun As Integer '定存變量

? Dim fuli_big As Long '大復(fù)利

? Dim fuli_small As Long '小復(fù)利

? Dim i As Integer '循環(huán)變量

? Dim DATAstring As String '數(shù)據(jù)字符串

? nianxian = Val(年限_TextBox.Text)

? dingcun = Val(定存_TextBox.Text)

? DATAstring = ""

? For i = 1 To nianxian

? ? ? fuli_small = dingcun * (1 + 0.1875)

? ? ? dingcun = fuli_small

? ? ? fuli_big = fuli_big + fuli_small

? ? ? DATAstring = DATAstring + "[" + Trim(Str(i)) + "]" + Str(fuli_big) + Chr(13) + Chr(10)

? ? ? 'DATAstring = DATAstring + "[" + Trim(Str(i)) + "]" + Str(fuli_small) + Chr(13) + Chr(10)

? Next

? 'fuli_big = fuli_small

? TextBox1.Text = DATAstring

? 結(jié)果_TextBox.Text = Str(fuli_big) + "元"

End Sub

VB.NET中的代碼

大概的過(guò)程：

Imports System.Data

Imports System.Data.SqlClient

--------------

Dim a As New SqlDataAdapter

Dim con As SqlConnection

con = New SqlConnection( "Persist Security Info=False;Integrated Security=SSPI;database=northwind;server=.;Connect Timeout=30")

con.Open()

a.SelectCommand = New SqlCommand("select * from table where c=1", con)

a.UpdateCommand = New SqlCommand("update table set b=2 where c=1", con)

a.DeleteCommand = New SqlCommand("delete from table where c=1", con)

a.InsertCommand = New SqlCommand("insert into table values (1,2,3)", con)

a.SelectCommand.ExecuteNonQuery()

a.UpdateCommand.ExecuteNonQuery()

a.DeleteCommand.ExecuteNonQuery()

a.InsertCommand.ExecuteNonQuery()

con.Close()

a.Dispose()