C# printed this

System.NullReferenceException: Object reference not set to an instance of an object.

What it meansYour code accessed a member on a reference that is null, so there was no object instance behind the variable at that moment.

The first thing to checkUse the stack trace line to find the null variable; common causes are uninitialized fields, failed lookups, and missing dependency injection.

The walrus saysThe most polite way to say null.