我想找到所有可以显式返回null的方法。
这可以在使用CQL的NDepend中实现吗？
答案 0 :(得分：2)
目前还没有，CQL到目前为止还不知道返回的变量，字段和值的值。
但是，建议使用以下默认规则。这个想法是，如果一个方法返回一个引用，它应该永远不为null，并且应该添加一个契约来断言它。如果您希望这样的方法返回null，请使用TryParse(string s, out T val):bool模式，例如// <Name>Public methods returning a reference needs a contract to ensure that a non-null reference is returned</Name>
warnif count > 0
let ensureMethods = Application.Methods.WithFullName(
"System.Diagnostics.Contracts.__ContractsRuntime.Ensures(Boolean,String,String)")
from ensureMethod in ensureMethods
from m in ensureMethod.ParentAssembly.ChildMethods where
m.IsPubliclyVisible &&
!m.IsAbstract &&
m.ReturnType != null &&
// Identify that the return type is a reference type
(m.ReturnType.IsClass || m.ReturnType.IsInterface) &&
!m.IsUsing(ensureMethod) &&
// Don't match method not implemented yet!
!m.CreateA("System.NotImplementedException".AllowNoMatch())
select new {
m,
ReturnTypeReference = m.ReturnType
}
//<Description>
// **Code Contracts** are useful to decrease ambiguity between callers and callees.
// Not ensuring that a reference returned by a method is *non-null* leaves ambiguity
// for the caller. This rule matches methods returning an instance of a reference type
// (class or interface) that don't use a **Contract.Ensure()** method.
//
// *Contract.Ensure()* is defined in the **Microsoft Code Contracts for .NET**
// library, and is typically used to write a code contract on returned reference:
// *Contract.Ensures(Contract.Result<ReturnType>() != null, "returned reference is not null");*
// https://visualstudiogallery.msdn.microsoft.com/1ec7db13-3363-46c9-851f-1ce455f66970
//</Description>
//<HowToFix>
// Use *Microsoft Code Contracts for .NET* on the public surface of your API,
// to remove most ambiguity presented to your client. Most of such ambiguities
// are about *null* or *not null* references.
//
// Don't use *null* reference if you need to express that a method might not
// return a result. Use instead the **TryXXX()** pattern exposed for example
// in the *System.Int32.TryParse()* method.
//</HowToFix>
。
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