How to avoid a NullReferenceException

问题

 if (alMethSign[z].ToString().Contains(aClass.Namespace))

Here, I load an exe or dll and check its namespace. In some dlls, there is no namespace, so aclass.namespace is not present and it's throwing a NullReferenceException.

I have to just avoid it and it should continue with rest of the code. If I use try-catch, it executes the catch part; I want it to continue with the rest of the code.

回答1:

Is aClass a Type instance? If so - just check it for null:

if (aClass != null && alMethSign[z].ToString().Contains(aClass.Namespace))

回答2:

Don't catch the exception. Instead, defend against it:

string nmspace = aClass.Namespace;

if (nmspace != null && alMethSign[z].ToString().Contains(nmspace))
{
    ...
}

回答3:

Add the test for null in the if statement.

if(aClass.NameSpace != null && alMethSign[z].ToString().Contains(aClass.Namespace))

回答4:

Or use an extension method to that checks for any nulls and either returns an empty string or the string value of the object:

public static string ToSafeString(this object o)
{
return o == null ? string.Empty : o.ToString();

}

来源：https://stackoverflow.com/questions/733383/how-to-avoid-a-nullreferenceexception