Question

我想使用Access 2017在ComboBox中进行自动完成。所以我使用了这段代码...但是有一些错误，比如：

“名称'da'在当前上下文中不存在”。

请帮我解决此错误。

    private void Autocomplete()
    {
        string query;
        OleDbConnection con = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|/Neth1.accdb");
        //opening connection
        con.Open();
        try
        {
            //initialize a new instance of sqlcommand
            OleDbCommand cmd = new OleDbCommand();
            //set a connection used by this instance of sqlcommand
            cmd.Connection = con;
            //set the sql statement to execute at the data source
            cmd.CommandText = query;

            OleDbDataAdapter da = new OleDbDataAdapter();
            //set the sql statement or stored procedure to execute at the data source
            da.SelectCommand = cmd;
            //initialize a new instance of DataTable
            DataTable dt = new DataTable();
            //add or resfresh rows in the certain range in the datatable to match those in the data source.
            da.Fill(dt);


            foreach (DataRow r in dt.Rows)
            {
                //getting all rows in the specific field|Column
                var rw = r.Field<string>("IMEI");


                //Set the properties of a combobox to make it auto suggest.
                comboBox1.AutoCompleteMode = AutoCompleteMode.Suggest;
                comboBox1.AutoCompleteSource = AutoCompleteSource.CustomSource;
                //adding all rows into the combobox
                comboBox1.AutoCompleteCustomSource.Add(rw);

            }
        }
        catch (Exception ex)
        {
            //catching error 
            MessageBox.Show(ex.Message);
        }
        //release all resources used by the component
          da.Dispose(); 
        //clossing connection
        con.Close();
    }

Answer 1

由于您使用的是try / catch块，我建议您包含con.Open（）。
打开连接也可能会失败。

当您处理oledb对象时，使用它也是一种健康的做法 {using blocks}，用于处理（）您创建的（一次性）对象。

你不想要的是在foreach循环中设置这些控件属性使用AddRage填充组合框AutoCompleteCustomSource也更有效，而不是每个角色添加一个对象。

这就是我建议编辑代码的方法：

//
comboBox1.AutoCompleteMode = AutoCompleteMode.SuggestAppend;
comboBox1.AutoCompleteSource = AutoCompleteSource.CustomSource;
//
string query = "SELECT SomeThing";
List<string> rw = new List<string>();

try
{
    using (OleDbConnection con = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|/Neth1.accdb"))
    {
        con.Open();
        using (OleDbCommand oCmd = new OleDbCommand(query, con))
        {
            using (OleDbDataReader _reader = oCmd.ExecuteReader())
            {
                if (_reader.HasRows == false) { return; }

                 while (_reader.Read())
                 {
                    rw.Add((string)_reader["IMEI"]);
                 }
            }
        }
    }
}
catch (Exception ex) {
    MessageBox.Show(ex.Message);
}
     comboBox1.AutoCompleteCustomSource.Clear();
     comboBox1.AutoCompleteCustomSource.AddRange(rw.ToArray());
     rw = null;

Answer 2

您的OleDbDataAdapter da = new OleDbDataAdapter();位于try {}范围内且

da.Dispose();超出了该范围，请尝试将此行放在try {}范围内，或将OleDbDataAdapter da = new OleDbDataAdapter();移到try {}范围之外。

使用Access 2017在ComboBox中自动完成

2 个答案: