我如何从文本框中向数据库中插入值 [英] how i insert a value from textbox to database

问题描述

任何人都可以帮助我摆脱这种逻辑错误

该代码无法显示输出中的数据

any one can help me out from this logic error

this code can''t show the data in the output

dbp = "PROVIDER=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Users\Administrator\Documents\mydata.mdb;User Id=admin;Password=;"
        con.ConnectionString = dbp
        con.Open()


        sql = "select * from test";
        
        da = New OleDb.OleDbDataAdapter(sql, con)
        da.Fill(ds, "mydata")
        MsgBox("Database is now Open")

        con.Close()
        MsgBox("Database is Now Closed")

[Edited]代码包装在"pre"标签中[/Edited]

code is wrapped in "pre" tags[/Edited]

推荐答案

我看不到该代码中的错误，但我可以看到一些不好的做法.

我是说.

如果您使用的是DataAdapter，则无需关闭连接，DataAdapter将对此完全负责.

调用da.Fill(ds,"mydata");
时数据将被填充 之后，数据库连接将关闭.并说数据库现在已打开"，然后又关闭了已经关闭的连接.

为了安全地关闭连接，您应该使用.

I can''t see error in that code but I can see some bad practice.

I mean.

If you''re using DataAdapter then no need to close connection, DataAdapter will be fully responsible for that.

Data Will be filled when you are calling da.Fill(ds,"mydata");
After that Database connection will be closed. and you stated that "Database is now open" and Further you closed again connection which is already closed.

For safe side to close connection you should use.

if (con.State == ConnectionState.Open)
 con.close();

好吧，以上代码只是从数据库中获取数据并将其填充到数据集中.没有其他的.您放置一个消息框以显示一些消息.没有编写任何代码来显示获取的数据.

正确地说，这是理解上的逻辑错误.如果需要查看获取的数据，然后将其作为示例，请在页面上放置一个网格，然后将获取的数据集绑定到该网格.检索到的数据将在此网格中可见.

Well, the above code just brings data from database and fills it in a dataset. Nothing else. You put a messagebox to display some message. There is no code written to display the data fetched.

As correctly said, it''s a logical error in understanding. If you need to see the data fetched then for sample, place a grid on the page and then bind the dataset fetched to this grid. Data retrieved would be visible in this grid.

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