WCF错误作为对象引用未设置为对象的实例 [英] WCF Error as object reference not set to an instance of an object

问题描述

在创建WCFService和LINQ时，在此行获取错误对象引用未设置为对象的实例。

getting Error "Object reference not set to an instance of an object" at this line while creating WCFService and LINQ..

base(global::System.Configuration.ConfigurationManager.ConnectionStrings["MySampleDBConnectionString1"].ConnectionString, mappingSource)

推荐答案

最有可能的原因是你的配置文件中没有名为 MySampleDBConnectionString1 的连接字符串。

The likeliest reason is that you don't have a connection string named MySampleDBConnectionString1 in your config file.

那是因为您的任何一个参数都是 null 。对我来说，第二个参数更有可能为null;因为通常你已经填充了ConnectionString属性，或者其中任何一个属性，连接字符串都不可用。



因此，如果您使用的是Visual Studio，请调试在此位置设置断点的代码。然后，一旦您的代码到达此位置，您将看到哪些情况属实;代码中哪个变量为null。然后，您可以（在调用基类的构造函数的特定行之上）将值设置为非null值以最小化此问题。



请记住，WCF也运行在.NET框架上，因此它会抛出的错误很容易像其他所有.NET异常一样处理。 NullReferenceException [ ^ ]是.NET框架的一个例外，初学者总是倾向于它，因为找到哪个对象扔掉它有点棘手，以及抛出它的原因。祝你好运。

That is because either of your parameters are null. For me, the second parameter has a more chance of being null; because usually you've already filled the ConnectionString property, or either of it, the connection string is not available.

So, if you're using Visual Studio, debug the code having a breakpoint set at this position. Then once your code reaches this location, you will see which of the cases is true; which variable is null in your code. Then you can (above that particular line of invoking the base-class's constructor) set the value to a non-null value to minimize this problem.

Remember, WCF also runs over .NET framework, so an error that it would throw would be easily handled as all other .NET exceptions. NullReferenceException[^] is an exception of .NET framework, and beginners always fall for it as it is a bit tricky to find which object threw this, and why it was thrown. Good luck.

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