c# - 填充 : SelectCommand. 连接属性尚未初始化。该怎么办？

Question

当我尝试使用方法 GetCities() 时，它说:

Fill: SelectCommand.Connection property has not been initialized.

谁能告诉我该怎么做？

public class CitiesService
{
    public DataSet DS;
    public OleDbConnection myConnection;
    public OleDbDataAdapter adapter;
    public OleDbDataAdapter adapter2;

    public CitiesService()
    {   
    }

    public DataSet GetCities()
    {
        OleDbCommand myCmd = new OleDbCommand("SPtblCities", myConnection);
        myCmd.CommandType = CommandType.StoredProcedure;
        OleDbDataAdapter Adapter = new OleDbDataAdapter();
        Adapter.SelectCommand = myCmd;
        DataSet dataSet = new DataSet();

        try
        {
            Adapter.Fill(dataSet, "tblCities");
            dataSet.Tables["tblCities"].PrimaryKey = new DataColumn[]
            { 
                dataSet.Tables["tblCities"].Columns["CityID"]
            };
        }
        catch (OleDbException ex)
        {
            throw ex;
        }

        return dataSet;
    }

}

Answer 1

是的，连接没有初始化，它是null。

替换

public OleDbConnection myConnection;

与

public OleDbConnection myConnection = new OleDbConnection(ConnectionString);

或者在方法中:

myConnection = new OleDbConnection(ConnectionString);
OleDbCommand myCmd = new OleDbCommand("SPtblCities", myConnection);