revert

analyzers/src/SonarAnalyzer.CSharp/Rules/AspNet/AvoidUnderPosting.cs

@@ -60,7 +60,8 @@ public sealed class AvoidUnderPosting : SonarDiagnosticAnalyzer
 
     private static void ProcessControllerMethods(SonarSyntaxNodeReportingContext context, ConcurrentDictionary<ITypeSymbol, bool> examinedTypes)
     {
-        if (context.SemanticModel.GetDeclaredSymbol(context.Node) is IMethodSymbol method && method.IsControllerActionMethod())
+        if (context.SemanticModel.GetDeclaredSymbol(context.Node) is IMethodSymbol method
+            && method.IsControllerActionMethod())
         {
             var modelParameterTypes = method.Parameters
                 .Where(x => !HasValidateNeverAttribute(x))
@@ -97,7 +98,8 @@ private static void CheckInvalidProperties(INamedTypeSymbol parameterType, Sonar
         && (type.Constructors.Any(x => x.Parameters.Length == 0)        // The type must have a parameterless constructor, unless
             || type.IsValueType                                         // - it's a value type
             || type.IsRecord()                                          // - it's a record type
-            || type.IsInterface());                                     // - it's an interface (although the type that implements will be actually used)
+            || type.IsInterface()                                       // - it's an interface (although the type that implements will be actually used)
+            || type.Is(KnownType.System_String));                       // - it has a custom Model Binder (e.g. System.String has one)
 
     private static bool CanBeNull(ITypeSymbol type) =>
         type is ITypeParameterSymbol { HasValueTypeConstraint: false }