wpf应用程序中的调用目标抛出了异常

我编写了一个简单的wpf应用程序来绑定datagrid中的数据。它在以下行运行时抛出错误。



string ConString = System.Configuration.ConfigurationManager

.ConnectionStrings [ConString]。ToString （）;

异常显示：调用目标抛出了异常。



InnerException：{对象引用未设置到一个对象的实例。}

I have written a simple wpf application for binding data in datagrid. It throws error while running at following line.

string ConString = System.Configuration.ConfigurationManager
.ConnectionStrings["ConString"].ToString();
Exception shows: Exception has been thrown by the target of an invocation."

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