gistfile1.cs

public static class ContextUtils
{
       public static void FixDateTimeColumns(DbContext context, DbModelBuilder modelBuilder)
       {
            var contextProps = context.GetType().GetProperties(BindingFlags.Instance | BindingFlags.Public);
            foreach (var contextProp in contextProps) {

                var propType = contextProp.PropertyType;

                if (!propType.IsGenericType)
                    continue;

                if (propType.GetGenericTypeDefinition()!=typeof(DbSet<>))
                    continue;

                var modelType = propType.GetGenericArguments()[0];
                
                // call generic Entity<> method
                var entityTypeConfig = modelBuilder.GetType().GetMethod("Entity").MakeGenericMethod(modelType).Invoke(modelBuilder, null);

                var modelProps = modelType.GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
                foreach (var modelProp in modelProps) {
                    var modelPropType = modelProp.PropertyType;
                    if (modelPropType != typeof(DateTime))
                        continue;

                    // prepare lambda (Expression<Func<TStructuralType, DateTime>>)
                    var typeParam = Expression.Parameter(modelType, "p");
                    var body = Expression.Property(typeParam, modelProp);
                    var lambda = Expression.Lambda(body, typeParam);

                    // call Property method
                    var propertyMethod = GetPropertyMethod(entityTypeConfig);
                    var propConfig = (DateTimePropertyConfiguration)propertyMethod.Invoke(entityTypeConfig, new[] { lambda });

                    // set the type
                    propConfig.HasColumnType("datetime2");
                }
            }
        }

        private static MethodInfo GetPropertyMethod(object entityTypeConfig)
        {
            foreach (var method in entityTypeConfig.GetType().GetMethods(BindingFlags.Instance | BindingFlags.Public)) {
                if (method.Name == "Property") {
                    var mParams = method.GetParameters();
                    if (mParams.Length == 1) {
                        var p = mParams[0];
                        var f = p.ParameterType.GetGenericArguments()[0]; // Func<TStructuralType, DateTime>
                        var args = f.GetGenericArguments();
                        if (args.Length == 2 && args[1] == typeof(DateTime)) {
                            return method;
                        }
                    }
                }
            }

            throw new InvalidOperationException("Could not find appropriate Property method.");
        }
}