Entity Framework Core Extensions: Getting Primary Keys and Dirty Properties

Two simple hacks: finding the primary key values:

public static IDictionary<string, object> GetKeys(this DbContext ctx, object entity)
{
if (ctx == null)
{
throw new ArgumentNullException(nameof(ctx));
}

if (entity == null)
{
throw new ArgumentNullException(nameof(entity));
}

var entry = ctx.Entry(entity);
var primaryKey = entry.Metadata.FindPrimaryKey();
var keys = primaryKey.Properties.ToDictionary(x => x.Name, x => x.PropertyInfo.GetValue(entity));

return keys;
}

This returns a dictionary because some entities may have composite primary keys.

As for getting the dirty (modified) properties’ names for an entity:

public static IEnumerable<string> GetDirtyProperties(this DbContext ctx, object entity)
{
if (ctx == null)
{
throw new ArgumentNullException(nameof(ctx));
}

if (entity == null)
{
throw new ArgumentNullException(nameof(entity));
}

var entry = ctx.Entry(entity);
var originalValues = entry.OriginalValues;
var currentValues = entry.CurrentValues;

foreach (var prop in originalValues.Properties)
{
if (object.Equals(originalValues[prop.Name], currentValues[prop.Name]) == false)
{
yield return prop.Name;
}
}
}
Picking on the last one, if we wish to reset an entity to it’s original values:
public static void Reset(this DbContext ctx, object entity)
{
if (ctx == null)
{
throw new ArgumentNullException(nameof(ctx));
}

if (entity == null)
{
throw new ArgumentNullException(nameof(entity));
}

var entry = ctx.Entry(entity);
var originalValues = entry.OriginalValues;
var currentValues = entry.CurrentValues;

foreach (var prop in originalValues.Properties)
{
currentValues[prop.Name] = originalValues[prop.Name];
}

entry.State = EntityState.Unchanged;
}

Mind you, this one will not reset collections or references, just plain properties.

Hope it helps!

Published by

Ricardo Peres

Team Leader at Dixons Carphone. Microsoft MVP.

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