dotnet · apoorvdarshan · Feb 17, 2026 · Feb 18, 2026
@@ -7955,6 +7955,12 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
   <data name="WRN_UninitializedNonNullableBackingField_Title" xml:space="preserve">
     <value>Non-nullable property must contain a non-null value when exiting constructor. Consider adding the 'required' modifier, or declaring the property as nullable, or safely handling the case where 'field' is null in the 'get' accessor.</value>
   </data>
+  <data name="WRN_UninitializedNonNullableEvent" xml:space="preserve">
+    <value>Non-nullable {0} '{1}' must contain a non-null value when exiting constructor. Consider declaring the {0} as nullable.</value>
+  </data>
+  <data name="WRN_UninitializedNonNullableEvent_Title" xml:space="preserve">
+    <value>Non-nullable event must contain a non-null value when exiting constructor. Consider declaring the event as nullable.</value>
+  </data>
   <data name="IDS_FeatureFirstClassSpan" xml:space="preserve">
     <value>first-class Span types</value>
   </data>

@@ -2463,6 +2463,8 @@ internal enum ErrorCode
         ERR_CollectionRefLikeElementType = 9358,
         ERR_BadCollectionArgumentsArgCount = 9359,
 
+        WRN_UninitializedNonNullableEvent = 9360,
+
         // Note: you will need to do the following after adding errors:
         //  1) Update ErrorFacts.IsBuildOnlyDiagnostic (src/Compilers/CSharp/Portable/Errors/ErrorFacts.cs)
         //  2) Add message to CSharpResources.resx

@@ -84,6 +84,7 @@ static ErrorFacts()
             nullableWarnings.Add(GetId(ErrorCode.WRN_NullabilityMismatchInParameterTypeOnInterceptor));
 
             nullableWarnings.Add(GetId(ErrorCode.WRN_UninitializedNonNullableBackingField));
+            nullableWarnings.Add(GetId(ErrorCode.WRN_UninitializedNonNullableEvent));
 
             NullableWarnings = nullableWarnings.ToImmutable();
         }
@@ -568,6 +569,7 @@ internal static int GetWarningLevel(ErrorCode code)
                 case ErrorCode.WRN_PartialMemberSignatureDifference:
                 case ErrorCode.WRN_FieldIsAmbiguous:
                 case ErrorCode.WRN_UninitializedNonNullableBackingField:
+                case ErrorCode.WRN_UninitializedNonNullableEvent:
                 case ErrorCode.WRN_AccessorDoesNotUseBackingField:
                 case ErrorCode.WRN_UnscopedRefAttributeOldRules:
                 case ErrorCode.WRN_RedundantPattern:
@@ -2477,6 +2479,7 @@ or ErrorCode.ERR_CannotApplyOverloadResolutionPriorityToOverride
                 or ErrorCode.ERR_CannotApplyOverloadResolutionPriorityToMember
                 or ErrorCode.ERR_PartialPropertyDuplicateInitializer
                 or ErrorCode.WRN_UninitializedNonNullableBackingField
+                or ErrorCode.WRN_UninitializedNonNullableEvent
                 or ErrorCode.WRN_UnassignedInternalRefField
                 or ErrorCode.WRN_AccessorDoesNotUseBackingField
                 or ErrorCode.ERR_IteratorRefLikeElementType

@@ -823,7 +823,9 @@ void checkMemberStateOnConstructorExit(MethodSymbol constructor, Symbol member,
                     : NullableFlowState.MaybeNull;
                 if (memberState >= badState) // is 'memberState' as bad as or worse than 'badState'?
                 {
-                    var errorCode = usesFieldKeyword ? ErrorCode.WRN_UninitializedNonNullableBackingField : ErrorCode.WRN_UninitializedNonNullableField;
+                    var errorCode = usesFieldKeyword ? ErrorCode.WRN_UninitializedNonNullableBackingField
+                        : symbol.Kind == SymbolKind.Event ? ErrorCode.WRN_UninitializedNonNullableEvent
+                        : ErrorCode.WRN_UninitializedNonNullableField;
                     var info = new CSDiagnosticInfo(errorCode, new object[] { symbol.Kind.Localize(), symbol.Name }, ImmutableArray<Symbol>.Empty, additionalLocations: symbol.Locations);
                     Diagnostics.Add(info, exitLocation ?? symbol.GetFirstLocationOrNone());
                 }