问题描述
复制 [克隆] LINQ to SQL 实体从而在数据库中生成新记录的最佳实践是什么?
What would be considered the best practice in duplicating [cloning] a LINQ to SQL entity resulting in a new record in the database?
上下文是我希望为管理员网格中的记录创建一个重复的函数.网站并在尝试了一些显而易见的事情后,读取数据,更改 ID=0,更改名称,submitChanges(),然后遇到异常,哈哈.我想我可能会停下来问问专家.
The context is that I wish to make a duplicate function for records in a grid of an *****. website and after trying a few things and the obvious, read data, alter ID=0, change name, submitChanges(), and hitting an exception, lol. I thought I might stop and ask an expert.
我希望首先读取记录,通过添加前缀Copy Of"更改名称,然后另存为新记录.
I wish to start with first reading the record, altering the name by prefixing with "Copy Of " and then saving as a new record.
推荐答案
创建一个新实例,然后使用 linq 映射类和反射来复制成员值.
Create a new instance and then use the linq mapping classes together with reflection to copy member values.
例如
public static void CopyDataMembers(this DataContext dc, object sourceEntity, object targetEntity) { //get entity members IEnumerable<MetaDataMember> dataMembers = from mem in dc.Mapping.GetTable(sourceEntity.GetType()) .RowType.DataMembers where mem.IsAssociation == false select mem; //go through the list of members and compare values foreach (MetaDataMember mem in dataMembers) { object originalValue = mem.StorageAccessor.GetBoxedValue(targetEntity); object newValue = mem.StorageAccessor.GetBoxedValue(sourceEntity); //check if the value has changed if (newValue == null && originalValue != null || newValue != null && !newValue.Equals(originalValue)) { //use reflection to update the target System.Reflection.PropertyInfo propInfo = targetEntity.GetType().GetProperty(mem.Name); propInfo.SetValue(targetEntity, propInfo.GetValue(sourceEntity, null), null); // setboxedvalue bypasses change tracking - otherwise // mem.StorageAccessor.SetBoxedValue(ref targetEntity, newValue); // could be used instead of reflection } } }
...或者您可以使用 DataContractSerializer 克隆它:
...or you can clone it using the DataContractSerializer:
internal static T CloneEntity<T>(T originalEntity) where T : someentitybaseclass { Type entityType = typeof(T); DataContractSerializer ser = new DataContractSerializer(entityType); using (MemoryStream ms = new MemoryStream()) { ser.WriteObject(ms, originalEntity); ms.Position = 0; return (T)ser.ReadObject(ms); } }