注册代码(防止用户名重复)

[andywsy]

在这里面怎么添代码啊?就是数据库里已经有了该用户名,别人用该用户名注册的时候怎么让它报错呢?vb.net
Try
conn.Open()
cmd.ExecuteNonQuery()
Panel2.Visible = True
Catch
Label1.Text = "注册失败"
Finally
conn.Close()
End Try

[a854468521]

[Quote=引用楼主 andywsy 的帖子:]
在这里面怎么添代码啊?就是数据库里已经有了该用户名,别人用该用户名注册的时候怎么让它报错呢?vb.net
Try
conn.Open()
cmd.ExecuteNonQuery()
Panel2.Visible = True
Catch
Label1.Text = "注册失败"
Finally
conn.Close()
End Try
[/Quote]
你可以在写入前先判断该数据库是否有该记录,然后在进入下步.

[andywsy]

具体怎么编呢?
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim dsn As String = ConfigurationSettings.AppSettings("DSN_student")
Dim conn As New SqlClient.SqlConnection
conn.ConnectionString = dsn
Dim cmd As New SqlClient.SqlCommand
cmd.Connection = conn
cmd.CommandText = "insert into Student_login (s_id,sl_name,sl_pwd,sl_phone,sl_date,sl_mailbox,sl_memo) values ('" + number.Text + "','" + realname.Text + "','" + password1.Text + "','" + phone.Text + "','" + DateTime.Now.Date + "','" + email.Text + "','" + memo.Text + "')"
Try
conn.Open()
cmd.ExecuteNonQuery()
Panel2.Visible = True
Catch
Label1.Text = "注册失败"
Finally
conn.Close()
End Try

End Sub

[a854468521]

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

Dim dsn As String = ConfigurationSettings.AppSettings("DSN_student")
Dim conn As New SqlClient.SqlConnection
conn.ConnectionString = dsn
Dim cmd As New SqlClient.SqlCommand
cmd.Connection = conn
cmd.CommandText ="select count(id) form Student_login "
if cmd.ExecuteScalar > 0 then
msgbox "错误"
exit sub
cmd.CommandText = "insert into Student_login (s_id,sl_name,sl_pwd,sl_phone,sl_date,sl_mailbox,sl_memo) values ('" + number.Text + "','" + realname.Text + "','" + password1.Text + "','" + phone.Text + "','" + DateTime.Now.Date + "','" + email.Text + "','" + memo.Text + "')"
Try
conn.Open()
cmd.ExecuteNonQuery()
Panel2.Visible = True
Catch
Label1.Text = "注册失败"
Finally
conn.Close()
End Try

End Sub

[a854468521]

Dim dsn As String = ConfigurationSettings.AppSettings("DSN_student")
Dim conn As New SqlClient.SqlConnection
conn.ConnectionString = dsn
Dim cmd As New SqlClient.SqlCommand
cmd.Connection = conn
cmd.CommandText = "select count(id) form Student_login where l_name '" & "????" & "'"
If cmd.ExecuteScalar > 0 Then
MsgBox("已经存在的用户.")
Exit Sub
End If
cmd.CommandText = "insert into Student_login (s_id,s,sl_pwd,sl_phone,sl_date,sl_mailbox,sl_memo) values ('" + number.Text + "','" + realname.Text + "','" + password1.Text + "','" + phone.Text + "','" + DateTime.Now.Date + "','" + email.Text + "','" + memo.Text + "')"
Try
conn.Open()
cmd.ExecuteNonQuery()
Panel2.Visible = True
Catch
Label1.Text = "注册失败"
Finally
conn.Close()
End Try


不意思,刚才没在IDE中写错了.

[andywsy]

if cmd.ExecuteScalar > 0 then 有错啊?

[andywsy]

错误说明:ExecuteReader 需要打开的并且可用的连接。该连接的当前状态是 Closed。

[a854468521]

If conn .State = ConnectionState.Closed Then conn .Open()

[a854468521]

数据库连接的开闭最好少用,耗时耗资源.

[andywsy]

放哪里啊?谢谢