C# example of optimistic concurrency with Entity Framework code first

2 minute read

The following article shows the good example how to use optimistic concurrency control in Entity Framework code first.\
http://msdn.microsoft.com/en-us/data/jj592904.aspx

Just in case I would like to copy the code examples from the above page.\
Resolving optimistic concurrency exceptions as client wins\

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using (var context = new BloggingContext())
{
    var blog = context.Blogs.Find(1);
    blog.Name = "The New ADO.NET Blog";
    bool saveFailed;
    do
    {
        saveFailed = false;
        try
        {
            context.SaveChanges();
        }
        catch (DbUpdateConcurrencyException ex)
        {
            saveFailed = true;
            // Update original values from the database
            var entry = ex.Entries.Single();
            entry.OriginalValues.SetValues(entry.GetDatabaseValues());
        }
    } while (saveFailed);
}
``` Resolving optimistic concurrency exceptions with Reload (database wins)\

using (var context = new BloggingContext())
{
var blog = context.Blogs.Find(1);
blog.Name = “The New ADO.NET Blog”;
bool saveFailed;
do
{
saveFailed = false;
try
{
context.SaveChanges();
}
catch (DbUpdateConcurrencyException ex)
{
saveFailed = true;
// Update the values of the entity that failed to save from the store
ex.Entries.Single().Reload();
}
} while (saveFailed);
}

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Custom resolution of optimistic concurrency exceptions\

using (var context = new BloggingContext())
{
var blog = context.Blogs.Find(1);
blog.Name = “The New ADO.NET Blog”;
bool saveFailed;
do
{
saveFailed = false;
try
{
context.SaveChanges();
}
catch (DbUpdateConcurrencyException ex)
{
saveFailed = true;
// Get the current entity values and the values in the database
var entry = ex.Entries.Single();
var currentValues = entry.CurrentValues;
var databaseValues = entry.GetDatabaseValues();
// Choose an initial set of resolved values. In this case we
// make the default be the values currently in the database.
var resolvedValues = databaseValues.Clone();
// Have the user choose what the resolved values should be
HaveUserResolveConcurrency(currentValues, databaseValues, resolvedValues);
// Update the original values with the database values and
// the current values with whatever the user choose.
entry.OriginalValues.SetValues(databaseValues);
entry.CurrentValues.SetValues(resolvedValues);
}
} while (saveFailed);
}
public void HaveUserResolveConcurrency(DbPropertyValues currentValues,
DbPropertyValues databaseValues,
DbPropertyValues resolvedValues)
{
// Show the current, database, and resolved values to the user and have
// them edit the resolved values to get the correct resolution.
}
``` Custom resolution of optimistic concurrency exceptions using objects\

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using (var context = new BloggingContext())
{
    var blog = context.Blogs.Find(1);
    blog.Name = "The New ADO.NET Blog";
    bool saveFailed;
    do
    {
        saveFailed = false;
        try
        {
            context.SaveChanges();
        }
        catch (DbUpdateConcurrencyException ex)
        {
            saveFailed = true;
            // Get the current entity values and the values in the database
            // as instances of the entity type
            var entry = ex.Entries.Single();
            var databaseValues = entry.GetDatabaseValues();
            var databaseValuesAsBlog = (Blog)databaseValues.ToObject();
            // Choose an initial set of resolved values. In this case we
            // make the default be the values currently in the database.
            var resolvedValuesAsBlog = (Blog)databaseValues.ToObject();
            // Have the user choose what the resolved values should be
            HaveUserResolveConcurrency((Blog)entry.Entity,
                                       databaseValuesAsBlog,
                                       resolvedValuesAsBlog);
            // Update the original values with the database values and
            // the current values with whatever the user choose.
            entry.OriginalValues.SetValues(databaseValues);
            entry.CurrentValues.SetValues(resolvedValuesAsBlog);
        }
    } while (saveFailed);
}
public void HaveUserResolveConcurrency(Blog entity,
                                       Blog databaseValues,
                                       Blog resolvedValues)
{
    // Show the current, database, and resolved values to the user and have
    // them update the resolved values to get the correct resolution.
}

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