从数据库获取数据到ComboBox

Short one.

A database named ComDet , and column cID(PK) , cName , cDet , mainCate(FK) , Subcat(FK).

一个名为ComDet的数据库,以及列cID(PK),cName,cDet,mainCate(FK),Subcat(FK)。

this suppose to get the data from table ComDet to the combobox..

这假设从表ComDet获取数据到组合框..

DataSet ds2;

private void searchBtn_Click(object sender, EventArgs e)
{
    SqlConnection conn = new SqlConnection();
    conn.ConnectionString = "Data Source=.\SQLEXPRESS;Initial Catalog=master;Integrated Security=True";
    conn.Open();

    SqlDataAdapter daSearch = new SqlDataAdapter("SELECT cName FROM ComDet", conn);
    ds2 = new DataSet();
    daSearch.Fill(ds2, "daSearch");
    ListU.ValueMember = "cName";
    ListU.DataSource = ds2.Tables["ComDet"];
    ListU.DropDownStyle = ComboBoxStyle.DropDownList;
    ListU.Enabled = true;
}

but it didnt work.. where did i go wrong? The Data(cName) from database table ComDet is not shown in the combobox. –

但它没有用..我哪里出错了?数据库表ComDet中的数据(cName)未显示在组合框中。 -

2 个解决方案

#1

Problem : You are assigning database table name ComDet as DataSource but not DataTable Name daSearch to ComboBox.

问题:您将数据库表名称ComDet指定为DataSource,但未将DataTable Name daSearch指定为ComboBox。

Solution : you need to assign valid DataTable Name to ComboBox as Datasource.

解决方案:您需要将有效的DataTable Name作为数据源分配给ComboBox。

Replace This :

替换这个:

ListU.DataSource = ds2.Tables["ComDet"];

With This:

ListU.DataSource = ds2.Tables["daSearch"];

(or)

ListU.DataSource = ds2.Tables[0];

Complete Code:

DataSet ds2;

private void searchBtn_Click(object sender, EventArgs e)
{
SqlConnection conn = new SqlConnection();
conn.ConnectionString = "Data Source=.\SQLEXPRESS;Initial Catalog=master;Integrated Security=True";
conn.Open();

SqlDataAdapter daSearch = new SqlDataAdapter("SELECT cName FROM ComDet", conn);
ds2 = new DataSet();
daSearch.Fill(ds2, "daSearch");
ListU.ValueMember = "cName";
ListU.DataSource = ds2.Tables["daSearch"];
ListU.DropDownStyle = ComboBoxStyle.DropDownList;
ListU.Enabled = true;
}

#2

So the question asks how to get data from database to combobox. Personally, I find using the DataSet class to be unpreferable - it is quite prone to errors like the asker is experiencing here.

所以问题是如何从数据库获取数据到组合框。就个人而言,我发现使用DataSet类是不可取的 - 它很容易出现像提问者在这里遇到的错误。

Try this approach. Which reads all the cName into a List and binds the List to the ComboBox. Simple and readable code. The use of using statements also ensures that the unmanaged resources are released efficiently.

试试这种方法。它将所有cName读入List并将List绑定到ComboBox。简单易读的代码。 using语句的使用还可确保有效释放非托管资源。

private void searchBtn_Click(object sender, EventArgs e)
{
    var list = new List<string>();
    using (var conn = new SqlConnection())
    {
        conn.ConnectionString = 
            "Data Source=.\SQLEXPRESS;Initial Catalog=master;Integrated Security=True";
        conn.Open();
        using (var cmd = new SqlCommand("SELECT cName FROM ComDet", conn))
        {
            using (var reader = cmd.ExecuteReader())
            {
                while (reader.Read())
                {
                    list.Add(Convert.ToString(reader["cName"]));
                }
            }
        }
   }
   ListU.DataSource = new BindingSource(list, null);
   ListU.DropDownStyle = ComboBoxStyle.DropDownList;
   ListU.Enabled = true;
}

#1