我在打开数据读取器时遇到问题 [英] i have problem in opening datareader

问题描述

大家好，
我正在写一个有关leitnerbox的程序.在我的程序中，我想在数据库的表中搜索单词.我有一个文本框，代码在text_changed事件中.这是我的代码，然后是错误.

Hello All,
I''m writing a program about leitnerbox. In my program I want to search words in my table in data base. I have a text box and my codes are in text_changed event. Here is my code amd then the error.

Private Sub TextBoxX3_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBoxX3.TextChanged
       Dim objcmd As SqlCommand
       Dim sql As String
       If CheckBoxX2.Checked = True Then
           sql = "select * from leitnertable where word like '%" & TextBoxX3.Text & "%'"
       End If
       If CheckBoxX1.Checked = True Then
           sql = "select * from leitnertable where firstmeaning or secondmeaning like '%" & TextBoxX3.Text & "%'"
       End If
       objcmd = New SqlCommand(sql, con)
       If objcmd.Connection.State = ConnectionState.Closed Then objcmd.Connection.Open()
       Dim dr As SqlDataReader
       dr = objcmd.ExecuteReader
       While dr.Read
           Dim dt As New DataTable
           dt.Load(dr)
           DataGridView2.DataSource = dt
       End While
   End Sub

复选框1正在搜索意思，而复选框2正在搜索单词.
当我调试程序时，错误是:

Check box1 is searching in meaninngs and check box2 is searching in words.
When I debug the program yhe error is:

>在关闭阅读器后尝试调用Read的尝试无效.

Invalid attempt to call Read when reader is closed.

我不知道该怎么办.

请帮帮我.

在此先谢谢您.

I don''t know what to do.

Please help me.

Thanks in Advance.

推荐答案

您可以使用objcmd = New SqlCommand(sql,con)实例化SqlCommand，但在任何地方都不能将con声明为SqlConnection.它是Global变量还是Form Level变量，并且使用正确的ConnectionString正确声明了吗?

You instantiate your SqlCommand with objcmd = New SqlCommand(sql,con) but nowhere do you declare con as a SqlConnection. Is it a Global or Form Level variable, and is it declared properly, with the correct ConnectionString ?

您不应该调用DataReader.Read方法:在Command.ExecuteReader之后，您只需一次调用DataTable.Load，然后关闭DataReader.

You shouldn''t call the DataReader.Read method: after Command.ExecuteReader you have just to call once DataTable.Load and then close the DataReader.

检查您的SQLCONNECTION.有问题.

Check your SQLCONNECTION. There is the problem.

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