Using SQL bulk copy with your LINQ-to-SQL datacontext

Linq-to-SQL is great for many things but it doesn't do very well with huge amounts of inserts. Extending the data context partial class with the following though will do the trick. I also wrote about this here. All you need to do is to create your LINQ entities just as you usually do and call the BulkInsertAll method on the datacontext. Also, do not use this datacontext for anything else before doing the bulk insert. The connection string of the datacontext that we use to create the SQLConnection here loses its password after its first use for some reason and that makes it, obviously, a bit difficult to connect.

partial class MyDataContext
{
    partial void OnCreated()
    {
        CommandTimeout = 5 * 60;
    }

    public void BulkInsertAll<T>(IEnumerable<T> entities)
    {
        entities = entities.ToArray();

        string cs = Connection.ConnectionString;
        var conn = new SqlConnection(cs);
        conn.Open();

        Type t = typeof(T);

        var tableAttribute = (TableAttribute)t.GetCustomAttributes(
            typeof(TableAttribute), false).Single();
        var bulkCopy = new SqlBulkCopy(conn) { 
            DestinationTableName = tableAttribute.Name };

        var properties = t.GetProperties().Where(EventTypeFilter).ToArray();
        var table = new DataTable();
        
        foreach (var property in properties)
        {
            Type propertyType = property.PropertyType;
            if (propertyType.IsGenericType &&
                propertyType.GetGenericTypeDefinition() == typeof(Nullable<>))
            {
                propertyType = Nullable.GetUnderlyingType(propertyType);
            }

            table.Columns.Add(new DataColumn(property.Name, propertyType));
        }

        foreach (var entity in entities)
        {
            table.Rows.Add(properties.Select(
              property => GetPropertyValue(
              property.GetValue(entity, null))).ToArray());
        }

        bulkCopy.WriteToServer(table);
        conn.Close();
    }

    private bool EventTypeFilter(System.Reflection.PropertyInfo p)
    {
        var attribute = Attribute.GetCustomAttribute(p, 
            typeof (AssociationAttribute)) as AssociationAttribute;

        if (attribute == null) return true;
        if (attribute.IsForeignKey == false) return true; 
        
        return false;
    }

    private object GetPropertyValue(object o)
    {
        if (o == null)
            return DBNull.Value;
        return o;
    }
}