What It Means & How to Fix It

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Why You’re Seeing This Error

The C2681 error means you’re using dynamic_cast on a type that isn’t valid for runtime casting — either because it’s not polymorphic or not a pointer/reference to a class with virtual functions.

In simple terms, the compiler is saying:

“You can’t use dynamic_cast here — this type doesn’t support it.”

In UE5, you typically see this when:

• You try to use dynamic_cast on UE types that don’t support it
• You’re casting non-pointer types (like structs, basic types, or value types)
• You’re using dynamic_cast instead of UE5’s Cast<>, which is preferred for UObject-derived types

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Example Error Message

error C2681: 'FVector' : invalid expression type for dynamic_cast

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Example Code

cppCopyEditFVector Location = GetActorLocation();
auto Result = dynamic_cast<FVector*>(&Location); //  C2681

This throws the error because FVector is a plain struct, not a polymorphic class.

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How to Fix C2681 in UE5 – Step-by-Step

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1. Don’t Use dynamic_cast on Structs or Non-Polymorphic Types

Only use dynamic_cast on pointers or references to classes with at least one virtual function.

Fix (generic C++):

cppCopyEditclass Base { virtual void DoSomething(); };
class Derived : public Base {};

Base* BasePtr = new Derived();
Derived* DerivedPtr = dynamic_cast<Derived*>(BasePtr); //  Valid

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2. For UE5 Object Types, Use Cast<> Instead

UE5 provides Cast<T>() to safely cast between UObject-derived classes.

Wrong:

cppCopyEditAMyActor* MyActor = dynamic_cast<AMyActor*>(SomeActor); //  C2681 in UE5

Fix:

AMyActor* MyActor = Cast(SomeActor); //  UE5-style casting

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3. Avoid dynamic_cast on Value Types Like int, FVector, etc.

These aren’t class pointers and cannot be cast this way.

Wrong:

cppCopyEditint32 MyNumber = 5;
auto Casted = dynamic_cast<float*>(&MyNumber); // 

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Summary: How to Fix C2681 in UE5

Cause	Fix Example
Using dynamic_cast on struct/value type	Don’t use it — cast manually or redesign
Casting UE5 object types improperly	Use Cast<>() instead of dynamic_cast
Type lacks virtual function	Make base class polymorphic if needed