在c＃中使用Access数据库中的DataTable填充ComboBox [英] Filling ComboBox using DataTable from Access database in c#

问题描述

我在MS Access数据库中有一个两列表，并希望在ComboBox中填充其第二列，用户可以从中进行选择。我正在使用DataTable来做到这一点。代码如下：

  private   void  Form1_Load（ object  sender，EventArgs e）
 {
 OleDbConnection connect =  new  OleDbConnection（ @  Provider = Microsoft.ACE.OLEDB.12.0; Data Source = C ：\ Users\Anas\Dropbox\C＃Projects \ 2.Database\ClOsODb.accdb; Persist Security Info = False）; 
 connect.Open（）; 
 OleDbCommand cmd =  new  OleDbCommand（  select *来自课程编号和名称，连接）; 
 OleDbDataReader odr =  null ; 
 odr = cmd.ExecuteReader（）; 
 DataTable table =  new  DataTable（）; 
 table.Load（odr）; 
 course_Number_and_NameComboBox.DataSource = table; 
 course_Number_and_NameComboBox.BindingContext =  this  .BindingContext; 
 course_Number_and_NameComboBox.DisplayMember =  课程编号和名称; 
 course_Number_and_NameComboBox.ValueMember =   ID; 
 connect.Close（）; 
} 

然而，问题是当我运行应用程序时，ComboBox是空的！它没有被填满。任何人都可以帮助我，告诉我哪里错了，我该怎么办？非常感谢帮助。



此外，有人可以告诉我如何在选择时获取DataTable所选行的第一列中的值在ComboBox中（换句话说，当一个项目将在表格中一行的ComboBox - 第二列中选中时 - 我将如何知道在ComboBox中选择哪一行以及如何在第一列中获取该值同一行）？

解决方案

首先看一下sql命令

从课程编号和名称中选择* 

桌子的名称是什么？就SQL而言，它是课程和数字和名称只是抛出错误 - 这就是为什么你没有填充你的组合框。



如果你真的必须在表名中使用空格（=坏主意）那么你必须用方括号括起表名，所以查询变为

从[课程编号和名称]中选择* 

这同样适用于同名的列

 course_Number_and_NameComboBox.DisplayMember =   [课程编号和名称]; 

至于问题的第二部分，当在ComboBox中选择一行时， course_Number_and_NameComboBox.Selected Text 属性将被设置为可见文本（即 [课程编号和名称] 中的值）和 course_Number_and_NameComboBox.Selected 值 属性将设置为 ValueMember - 即 ID中的值

如果您想要数据表中的任何其他数据，则必须根据ID

更改

 OleDbCommand cmd =  new  OleDbCommand（   select * from Course Number and Name，connect）; 

to

 OleDbCommand cmd =  new  OleDbCommand（ 从[课程编号和名称]中选择Col1，ID，连接）; 

给出表中给出的列名，当表名或列名中有空格时也使用[]

然后，

 course_Number_and_NameComboBox.DisplayMember =   Col1; 
 course_Number_and_NameComboBox.ValueMember =   ID; 

I have a two column table in an MS Access database and want to fill its second column in a ComboBox from where the user can make a selection. I'm using a DataTable to do it. The code is below:

private void Form1_Load(object sender, EventArgs e)
{
    OleDbConnection connect = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0; Data         Source=C:\Users\Anas\Dropbox\C# Projects\2.Database\ClOsODb.accdb; Persist Security   Info=False");
    connect.Open();
    OleDbCommand cmd = new OleDbCommand("select * from Course Number and Name", connect);
    OleDbDataReader odr = null;
    odr = cmd.ExecuteReader();
    DataTable table = new DataTable();
    table.Load(odr);
    course_Number_and_NameComboBox.DataSource = table;
    course_Number_and_NameComboBox.BindingContext = this.BindingContext;
    course_Number_and_NameComboBox.DisplayMember = "Course Number and Name";
    course_Number_and_NameComboBox.ValueMember = "ID";
    connect.Close();
}

However, the problem is that when I run the application, the ComboBox is empty! It doesn't get filled. Can anyone help me and tell me where I am wrong and what should I do? Help will be greatly appreciated.

Also, can anyone tell me how will I get the value in the first column of the selected row of the DataTable when a selection is made at the ComboBox(in other words, when an item will be selected in the ComboBox-second column of a row in the table-how will I know which row is selected in the ComboBox and how will I get the value in the first column of the same row)?

解决方案

Firstly have a look at that sql command

select * from Course Number and Name

What is the name of the table? As far as SQL is concerned then it is "Course" and "Number and Name" just throw an error - which is why you don't get your combobox populated.

If you really must use spaces in your table names ( = bad idea ) then you must surround the table name with square brackets, so the query becomes

select * from [Course Number and Name]

The same applies to the column of the same name

course_Number_and_NameComboBox.DisplayMember = "[Course Number and Name]";

As to the second part of your question, when a row is selected in the ComboBox the course_Number_and_NameComboBox.SelectedText property will be set to the visible text (i.e. the value that was in [Course Number and Name]) and the course_Number_and_NameComboBox.SelectedValue property will be set to the ValueMember - i.e. the value that was in ID
If you want any other data from the datatable you will have to look it up based on the ID

change

OleDbCommand cmd = new OleDbCommand("select * from Course Number and Name", connect);

to

OleDbCommand cmd = new OleDbCommand("select Col1, ID from [Course Number and Name]", connect);

give the column names as you given in your table and also use [] when you have spaces in your table name or column names
then,

course_Number_and_NameComboBox.DisplayMember = "Col1";
course_Number_and_NameComboBox.ValueMember = "ID";

这篇关于在c＃中使用Access数据库中的DataTable填充ComboBox的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！