{“对象引用未设置为对象的实例。”}运行项目时出现错误

Question

开始运行项目时出现以下错误。 Plz帮助我。

{"Object reference not set to an instance of an object."}

我从

开始在以下代码段中得到提到的错误

    String connectionKRAcademy = ConfigurationManager.ConnectionStrings["ChequeRegistry"].ConnectionString;

class DataControl
    {
        String connectionKRAcademy = ConfigurationManager.ConnectionStrings["ChequeRegistry"].ConnectionString;
    public static oledbConnection NewCon;
    public oledbDataReader dr;
    public int dataread = 0;
    public DataControl()
    { }