public static Expression <Func <TSource, bool> > GetFilterExpression <TSource, TFilter>(TFilter filter)
{
List <ExpressionFilterModel> filters = new List <ExpressionFilterModel>();
PropertyInfo[] filterProps = typeof(TFilter).GetProperties();
foreach (PropertyInfo filterProperty in filterProps)
{
ExpressionFilterModel expression = new ExpressionFilterModel();
expression.Comparison = FilterComparison.Equal;
expression.Value = filterProperty.GetValue(filter);
if (expression.Value == null)
{
continue;
}
FilterAttribute attribute = (FilterAttribute)filterProperty.GetCustomAttributes(true).Where(x => x.GetType() == typeof(FilterAttribute)).FirstOrDefault();
if (attribute == null || attribute.FilterComparison == FilterComparison.NoFilter)
{
continue;
}
expression.Comparison = attribute.FilterComparison;
if (attribute.FilterProperty != null)
{
expression.PropertyName = attribute.FilterProperty;
}
else
{
expression.PropertyName = filterProperty.Name;
}
filters.Add(expression);
}
return(ConstructAndExpressionTree <TSource>(filters));
}
public static Expression GetExpression <T>(ParameterExpression param, ExpressionFilterModel filter)
{
if (filter.Value == null)
{
return(null);
}
Expression member = Expression.Property(param, filter.PropertyName);
Expression constant = Expression.Constant(filter.Value);
if (member.Type.Name.ToLower() != "string")
{
FilterForNullableMember(ref member, ref constant);
}
BinaryExpression exp = Expression.NotEqual(member, Expression.Constant(null));
Expression next = null;
switch (filter.Comparison)
{
case FilterComparison.Equal:
next = Expression.Equal(member, constant);
break;
case FilterComparison.GreaterThan:
next = Expression.GreaterThan(member, constant);
break;
case FilterComparison.GreaterThanOrEqual:
next = Expression.GreaterThanOrEqual(member, constant);
break;
case FilterComparison.LessThan:
next = Expression.LessThan(member, constant);
break;
case FilterComparison.LessThanOrEqual:
next = Expression.LessThanOrEqual(member, constant);
break;
case FilterComparison.NotEqual:
next = Expression.NotEqual(member, constant);
break;
case FilterComparison.Contains:
constant = Expression.Constant(((string)filter.Value).ToLower());
next = Expression.Call(member, containsMethod, constant);
break;
case FilterComparison.StartsWith:
constant = Expression.Constant(((string)filter.Value).ToLower());
next = Expression.Call(member, startsWithMethod, constant);
break;
case FilterComparison.EndsWith:
constant = Expression.Constant(((string)filter.Value).ToLower());
next = Expression.Call(member, endsWithMethod, constant);
break;
default:
return(null);
}
return(Expression.And(exp, next));
}
