Concatenate where queries with or operator in a QueryBuilder

QueryBuilder is defined in Microsoft.Windows.Data.DomainServices. It allows you to create a Query on a collection of type T and apply it later.

When I need to concatenate where queries by && it is easy, for example you can do

        var query = new QueryBuilder<Customer>();

        if (!string.IsNullOrEmpty(this.CustomerFirstName))
            query = query.Where(c => c.FirstName == this.CustomerFirstName);

        if (!string.IsNullOrEmpty(this.CustomerLastName))
            query = query.Where(c => c.LastName == this.CustomerLastName);

        if (!string.IsNullOrEmpty(this.CustomerPhone))
            query = query.Where(c => c.Phone == this.CustomerPhone);

        if (!string.IsNullOrEmpty(this.CustomerMail))
            query = query.Where(c => c.Mail == this.CustomerMail);

I can't find out how should I concatenate those Where queries by || (or)??

I have a query that loads all Products in a database, since products are organized by category and a user can select only a sub-set of categories (the one he is interested in) I would like to load only products in categories that the user has specified

I know I could do it concatenating Where() by && where I exclude unselected categories example

 query.Where(c => c.CategoryName != "MyCategory");

but I don't like it.

I would like to do it in a foreach loop

private void LoadProducts()
{
     var query = new QueryBuilder<Product>();

     //Get Only Products in specified categories
     if (!string.IsNullOrEmpty(WebContext.Current.User.SelectedCat开发者_StackOverflowegoriesCSV))
     {

         foreach (string cat in WebContext.Current.User.SelectedCategoriesCSV.Split(';'))
         {
               ????//query.Where(c => c.CategoryName == cat || );
         }

     }

 .....

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You need to dynamically build your where expression and then pass it once to the query.Where(). Check out the PredicateBuilder that provides Or method to accomplish that. Hope this helps.

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You can use Dynamic LINQ operator that are available at this link: http://msdn.microsoft.com/en-us/bb330936.aspx (download the c# example and get the code in the \LinqSamples\DynamicQuery directory)

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You can use PredicateBuilder class developed by Monty’s Gush.

Try this.