Szerkesztés

Megosztás a következőn keresztül:

ObjectContext.Refresh Method

  • Reference

Definition

Namespace:
System.Data.Objects
Assembly:
System.Data.Entity.dll

Updates specific objects in the object context with data from the data source.

Overloads

Refresh(RefreshMode, IEnumerable)

Updates a collection of objects in the object context with data from the data source.
Refresh(RefreshMode, Object)

Updates an object in the object context with data from the data source.

Remarks

The order in which objects are refreshed is nondeterministic.

Refresh(RefreshMode, IEnumerable)

Updates a collection of objects in the object context with data from the data source.

public:
 void Refresh(System::Data::Objects::RefreshMode refreshMode, System::Collections::IEnumerable ^ collection);
public void Refresh (System.Data.Objects.RefreshMode refreshMode, System.Collections.IEnumerable collection);
member this.Refresh : System.Data.Objects.RefreshMode * System.Collections.IEnumerable -> unit
Public Sub Refresh (refreshMode As RefreshMode, collection As IEnumerable)

Parameters

refreshMode
RefreshMode

A RefreshMode value that indicates whether property changes in the object context are overwritten with property values from the data source.

collection
IEnumerable

An IEnumerable collection of objects to refresh.

Exceptions

ArgumentNullException

collection is null.

ArgumentOutOfRangeException

refreshMode is not valid.

ArgumentException

collection is empty.

-or-

An object is not attached to the context.

Remarks

This method has the dual purpose of allowing objects in the object context to be refreshed with data from the data source, and being the mechanism by which conflicts can be resolved. For more information, see Saving Changes and Managing Concurrency.

The order in which objects are refreshed is nondeterministic.

After Refresh is called, the object's original values will always be updated with the data source value, but the current values might or might not be updated with the data source value. This depends on the RefreshMode value. The StoreWins mode means that the objects in the collection should be updated to match the data source values. ClientWins means that only the changes in the object context will be persisted, even if there have been other changes in the data source.

To ensure that objects have been updated by data source-side logic, you can call Refresh with StoreWins after you call the SaveChanges method.

See also

Applies to

Refresh(RefreshMode, Object)

Updates an object in the object context with data from the data source.

public:
 void Refresh(System::Data::Objects::RefreshMode refreshMode, System::Object ^ entity);
public void Refresh (System.Data.Objects.RefreshMode refreshMode, object entity);
member this.Refresh : System.Data.Objects.RefreshMode * obj -> unit
Public Sub Refresh (refreshMode As RefreshMode, entity As Object)

Parameters

refreshMode
RefreshMode

One of the RefreshMode values that specifies which mode to use for refreshing the ObjectStateManager.

entity
Object

The object to be refreshed.

Exceptions

ArgumentNullException

collection is null.

ArgumentOutOfRangeException

refreshMode is not valid.

ArgumentException

collection is empty.

-or-

An object is not attached to the context.

Examples

This example tries to save changes, and this may cause a concurrency conflict. Then it shows how to resolve the concurrency conflict by refreshing the object context before re-saving changes.

using (AdventureWorksEntities context =
    new AdventureWorksEntities())
{
    try
    {
        // Perform an operation with a high-level of concurrency.
        // Change the status of all orders without an approval code.
        ObjectQuery<SalesOrderHeader> orders =
            context.SalesOrderHeaders.Where(
            "it.CreditCardApprovalCode IS NULL").Top("100");

        foreach (SalesOrderHeader order in orders)
        {
            // Reset the order status to 4 = Rejected.
            order.Status = 4;
        }
        try
        {
            // Try to save changes, which may cause a conflict.
            int num = context.SaveChanges();
            Console.WriteLine("No conflicts. " +
                num.ToString() + " updates saved.");
        }
        catch (OptimisticConcurrencyException)
        {
            // Resolve the concurrency conflict by refreshing the
            // object context before re-saving changes.
            context.Refresh(RefreshMode.ClientWins, orders);

            // Save changes.
            context.SaveChanges();
            Console.WriteLine("OptimisticConcurrencyException "
            + "handled and changes saved");
        }

        foreach (SalesOrderHeader order in orders)
        {
            Console.WriteLine("Order ID: " + order.SalesOrderID.ToString()
                + " Order status: " + order.Status.ToString());
        }
    }
    catch (UpdateException ex)
    {
        Console.WriteLine(ex.ToString());
    }
}

Remarks

Refresh has the dual purpose of allowing an object to be refreshed with data from the data source and being the mechanism by which conflicts can be resolved. For more information, see Saving Changes and Managing Concurrency.

The order in which objects are refreshed is nondeterministic.

After the Refresh method is called, the object's original values will always be updated with the data source value, but the current values might or might not be updated with the data source value. This depends on the RefreshMode. The StoreWins mode means that the object should be updated to match the data source values. The ClientWins value means that only the changes in the object context will be persisted, even if there have been other changes in the data source.

To ensure that an object has been updated by data source-side logic, you can call the Refresh method with the StoreWins value after you call the SaveChanges method.

See also

Applies to