您是否可以说服DataContext将列视为总是脏的？

Question

有没有办法强制LINQ-to-SQL将列视为脏？在全球范围内就够了....

基本上,我在使用L2S与遗留系统进行一些审计代码时遇到了问题,想象一下:

var ctx = new SomeDataContext(); // disposed etc - keeping it simple for illustration
var cust = ctx.Customers.First(); // just for illustration
cust.SomeRandomProperty = 17; // whatever
cust.LastUpdated = DateTime.UtcNowl;
cust.UpdatedBy = currentUser;
ctx.SubmitChanges(); // uses auto-generated TSQL

这很好,但是如果同一个用户连续两次更新它,那么它UpdatedBy是一个NOP,而TSQL将是(粗略地):

UPDATE [dbo].[Customers]
SET SomeRandomColumn = @p0 , LastUpdated = @p1 -- note no UpdatedBy
WHERE Id = @p2 AND Version = @p3

在我的情况下,问题是目前所有表都有一个带括号审计触发器,它检查审计列是否已更新,如果不是假设开发人员有错(替换SUSER_SNAME(),尽管可能就像容易抛出错误一样).

我真正希望能够做的是"总是更新这个专栏,即使它不脏" - 这可能吗？

Answer 1

根据KristoferA的回答,我得到了类似下面的内容; 这是邪恶和脆弱的(经常是反思),但现在可能已经足够了.战斗的另一面是改变触发器的行为:

partial class MyDataContext // or a base-class
{
    public override void SubmitChanges(System.Data.Linq.ConflictMode failureMode)
    {
        this.MakeUpdatesDirty("UpdatedBy", "Updated_By");
        base.SubmitChanges(failureMode);
    }
}
public static class DataContextExtensions
{
    public static void MakeUpdatesDirty(
        this DataContext dataContext,
        params string[] members)
    {
        if (dataContext == null) throw new ArgumentNullException("dataContext");
        if (members == null) throw new ArgumentNullException("members");
        if (members.Length == 0) return; // nothing to do
        foreach (object instance in dataContext.GetChangeSet().Updates)
        {
            MakeDirty(dataContext, instance, members);
        }
    }
    public static void MakeDirty(
        this DataContext dataContext, object instance ,
        params string[] members)
    {
        if (dataContext == null) throw new ArgumentNullException("dataContext");
        if (instance == null) throw new ArgumentNullException("instance");
        if (members == null) throw new ArgumentNullException("members");
        if (members.Length == 0) return; // nothing to do
        const BindingFlags AllInstance = BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public;
        object commonDataServices = typeof(DataContext)
            .GetField("services", AllInstance)
            .GetValue(dataContext);
        object changeTracker = commonDataServices.GetType()
            .GetProperty("ChangeTracker", AllInstance)
            .GetValue(commonDataServices, null);
        object trackedObject = changeTracker.GetType()
            .GetMethod("GetTrackedObject", AllInstance)
            .Invoke(changeTracker, new object[] { instance });
        var memberCache = trackedObject.GetType()
            .GetField("dirtyMemberCache", AllInstance)
            .GetValue(trackedObject) as BitArray;

        var entityType = instance.GetType();
        var metaType = dataContext.Mapping.GetMetaType(entityType);
        for(int i = 0 ; i < members.Length ; i++) {
            var member = entityType.GetMember(members[i], AllInstance);
            if(member != null && member.Length == 1) {
                var metaMember = metaType.GetDataMember(member[0]);
                if (metaMember != null)
                {
                    memberCache.Set(metaMember.Ordinal, true);
                }
            }
        }
    }
}