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IVariantsProvider Interface

Implemented by objects that provide a list of view variants available for the specific View, and stores the variant selected by the user.

Namespace: DevExpress.ExpressApp.ViewVariantsModule

Assembly: DevExpress.ExpressApp.ViewVariantsModule.v18.2.dll

Declaration

public interface IVariantsProvider
Public Interface IVariantsProvider

Related API Members

The following members accept/return IVariantsProvider objects:

Remarks

The default implementation of the IVariantsProvider interface used by the View Variants Module is ModelVariantsProvider, that stores view variants in the Application Model. You can create a custom IVariantsProvider implementation and pass it to the ViewVariantsModule.VariantsProvider property.

The following snippet illustrates how to implement an IVariantsProvider that stores View Variants in the database.

public class DatabaseViewVariantsProvider : IVariantsProvider {
    XafApplication application;
    public DatabaseViewVariantsProvider(XafApplication application) {
        Guard.ArgumentNotNull(application, "application");
        this.application = application;
    }
    public VariantsInfo GetVariants(string rootVariantViewId) {
        VariantsInfo result = null;
        if(application.Security.IsAuthenticated) {
            using(IObjectSpace os = application.CreateObjectSpace(typeof(ViewVariantsObject))) {
                ViewVariantsObject variants = os.FindObject<ViewVariantsObject>(
                new BinaryOperator("RootViewId", rootVariantViewId));
                if(variants != null && (variants.Items.Count >= 2)) {
                    List<VariantInfo> items = new List<VariantInfo>();
                    foreach(ViewVariantObject variant in variants.Items) {
                        items.Add(new VariantInfo(variant.Oid.ToString(), variant.ViewId, variant.Caption));
                    }
                    string currentVariantId;
                    if(variants.CurrentVariant != null) {
                        currentVariantId = variants.CurrentVariant.Oid.ToString();
                    }
                    else {
                        currentVariantId = variants.Items[0].Oid.ToString();
                    }
                    result = new VariantsInfo(variants.RootViewId, currentVariantId, items);
                }
            }
        }
        return result;
    }
    public void SaveCurrentVariantId(string rootViewId, string currentVariantId) {
        using(IObjectSpace os = application.ObjectSpaceProvider.CreateObjectSpace()) {
            ViewVariantObject variant = os.GetObjectByKey<ViewVariantObject>(Guid.Parse(currentVariantId));
            if((variant == null) || (variant.Owner == null)) {
                throw new InvalidOperationException();
            }
            variant.Owner.CurrentVariant = variant;
            os.CommitChanges();
        }
    }
}

The following code illustrates persistent objects used by DatabaseViewVariantsProvider to store View Variants:

[DefaultClassOptions, XafDefaultProperty("RootViewId")]
public class ViewVariantsObject : BaseObject {
    public ViewVariantsObject(Session session) : base(session) { }
    [Indexed(Unique = true), RuleUniqueValue]
    public string RootViewId { 
        get { return GetPropertyValue<string>("RootViewId"); } 
        set { SetPropertyValue<string>("RootViewId", value); }
    }
    public ViewVariantObject CurrentVariant { 
        get { return GetPropertyValue<ViewVariantObject>("CurrentVariant"); } 
        set { SetPropertyValue<ViewVariantObject>("CurrentVariant", value); }
    }
    [Association]
    public XPCollection<ViewVariantObject> Items { 
        get { return GetCollection<ViewVariantObject>("Items"); }
    }
}
[XafDefaultProperty("Caption")]
public class ViewVariantObject : BaseObject {
    public ViewVariantObject(Session session) : base(session) { }
    [Association]
    public ViewVariantsObject Owner { 
        get { return GetPropertyValue<ViewVariantsObject>("Owner"); } 
        set { SetPropertyValue<ViewVariantsObject>("Owner", value); }
    }
    public string ViewId { 
        get { return GetPropertyValue<string>("ViewId"); }
        set { SetPropertyValue<string>("ViewId", value); } 
    }
    public string Caption { 
        get { return GetPropertyValue<string>("Caption"); } 
        set { SetPropertyValue<string>("Caption", value); } 
    }
}
See Also