how to make a method async with async and awit : i understand the use of async and await and when see any method using can understand easily but not able to make it self.          

    public static Expression<Func<T, bool>> GetExpression<T>(Field filter)
                        {
                            ParameterExpression param = Expression.Parameter(typeof(T), "t");
                            Expression exp = null;
                            if (filter != null)
                            {
                                exp = GetExpression<T>(param, filter);
                            }
                
                            return Expression.Lambda<Func<T, bool>>(exp, param);
                        }
                 
                private static Expression GetExpression<T>(ParameterExpression param,Field filter)
                        {
                            var stringMember = Expression.Call(asString, Expression.Convert(member, typeof(object)));
                            ConstantExpression constant = Expression.Constant(filter.TextToBeFiltered.ToString().ToLower());
                
                            switch (filter.Operation)
                            {
                                case FilterEnum.Equals:
                                    return Expression.Equal(stringMember, constant);
                
                                case FilterEnum.DoesNotEqual:
                                    return Expression.NotEqual(stringMember, constant);  
                
                            }    
                            return null;
                        }

how to make these methods as async using async and await
