BindingSource.Find Multiple Columns

Question

Is it possible to use the Find method of a BindingSource on multiple columns?

For example, say I have a gridview displaying current pets; two comboboxes, cboPetType and cboGender; and a button to create a new record into the Pet table based on the values of these two comboboxes.

Now, let's say I only want one of each PetType/Gender combination (Dog - M, Cat - F, etc.). So, if I have a Dog - M pet in my BindingSource and a user selects Dog and M from the comboboxes, I would like to stop the user to inform them that combination already exists.

In the past, I have used the BindingSource.Find method to do something similar, but, as far as I can tell, that is only good for searching one column (i.e. BindingSource.Find("PetType", cboPetType.SelectedValue);).

Is it possible to search a bindingsource based on multiple columns? If not, any suggestions to achieve my desired result? Any advice is greatly appreciated!

Answer 1

No, unfortunately this isn't possible. While it's likely that given a particular data source that such a search would be fairly simple, doing it in a more generic way (as the BindingSource would) is a little less transparent. For one, the syntax would be less than obvious. Here's a somewhat contrived solution:

public class Key
{
    public string PropertyName {get; set;}
    public object Value {get; set;}
}

public static int Find(this BindingSource source, params Key[] keys)
{
    PropertyDescriptor[] properties = new PropertyDescriptor[keys.Length];

    ITypedList typedList = source as ITypedList;

    if(source.Count <= 0) return -1;

    PropertyDescriptorCollection props;

    if(typedList != null) // obtain the PropertyDescriptors from the list
    {
        props = typedList.GetItemProperties(null);
    }
    else // use the TypeDescriptor on the first element of the list
    {
        props = TypeDescriptor.GetProperties(source[0]);
    }

    for(int i = 0; i < keys.Length; i++)
    {
        properties[i] = props.Find(keys[i].PropertyName, true, true); // will throw if the property isn't found
    }

    for(int i = 0; i < source.Count; i++)
    { 
        object row = source[i];
        bool match = true;

        for(int p = 0; p < keys.Count; p++)
        {
            if(properties[p].GetValue(row) != keys[p].Value))
            {
                match = false;
                break;
            }
        }

        if(match) return i;
    }

    return -1;
}

You can call it like this:

BindingSource source = // your BindingSource, obviously 

int index = source.Find(
    new Key { PropertyName = "PetType", Value = "Dog" },
    new Key { PropertyName = "Gender", Value = "M" });

Bear in mind that for this to be usable, you really need a smarter comparison algorithm, but I'll leave that as an exercise to the reader. Checking for an implementation of IComparable would be a good start. Nonetheless, the concept should carry through regardless of that particular point of implementation.

Note that this won't take advantage of any of the possible performance optimizations that might be implemented by the underlying data source, whereas the single column Find would.

Answer 2

Another simpler solution, in case someone runs into the same issue. This works when the BindingSource is a DataView:

MyBindingSource.Sort = "Column1,Column2"
Dim underlyingView As DataView = DirectCast(MyBindingSource.List, DataView)
Dim searchVals As New List(Of Object)
searchVals.Add("SearchString1")
searchVals.Add("SearchString2")

Dim ListIndex as Integer = underlyingView.Find(searchVals.ToArray)

If ListIndex >=0 Then
    MyBindingList.Position = ListIndex
Else
    'No matches, so what you need to do...
End If