Multiple where conditions in EF [duplicate]

Answer 1

The flexible way to do this is to build up the where clause separately.

This article shows you how to do that. It takes a bit of work to initially set it up. But its worth it.

Answer 2

Take a look at PredicateBuilder. It will allow you to do something like this:

IQueryable<??> SearchProducts (params string[] keywords)
{
  var predicate = PredicateBuilder.True<??>();

  foreach (string keyword in keywords)
  {
    string temp = keyword;
    if(temp != String.Empty || temp != "All")
          predicate = predicate.And(e => e.???.Contains (temp));
  }
  return dataContext.??.Where (predicate);
}

Note:

Answer 3

Assuming that Location and Category are identified in your code by ids (id is the value attribute in the comboboxes items), you can do something similar to

function GetItems(string keyword, string consultant, int? locationId, int categoryId){

using(MyContextEntities context = new MyContextEntities()){
    return context.Items.Where(item => 
        (string.IsNullOrEmpty(keyword) || item.Text.Contains(keyword))
        && (string.IsNullOrEmpty(consultant) || item.Consultant.Contains(consultant))
        && (!locationId.HasValue || item.Location.Id == locationId.Value)
        && (!categoryId.HasValue || item.Category.Id == categoryId.Value)
    );
}
}

Answer 4

I think Skip While and Take While may help in your situation

http://msdn.microsoft.com/en-us/vcsharp/aa336757#SkipWhileSimple

Answer 5

You can chain your where clauses. You just need an IQueryable datasource.

var filteredData = _repository.GetAll();
//If your data source is IEnumerable, just add .AsQueryable() to make it IQueryable

if(keyWordTextBox.Text!="")
    filteredData=filteredData.Where(m=>m.Keyword.Contains(keyWordTextBox.Text));

if(LocationDropDown.SelectedValue!="All")
    filteredData=filteredData.Where(m=>m.Location==LocationDropDown.SelectedValue));

... etc....

Because it is IQueryable, the data is not fetched until you bind it so it only pulls the data you need.

Answer 6

You can do something like this.

var abc = from al in myEntity.a
                  where (field == string.Empty ? al.field == string.Empty : al.field == field)
                  select new { al.field1, al.field2, al.field3 };