问题描述

有没有办法强制 LINQ-to-SQL 将列视为脏列?在全球范围内就足够了....

Is there a way to force LINQ-to-SQL to treat a column as dirty? Globally would suffice....

基本上，我在与 L2S 交谈的遗留系统上的一些审计代码有问题，想象一下:

Basically, I've got a problem with some audit code on a legacy system that I'm talking to with L2S, imagine:

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，但如果同一用户连续更新两次，UpdatedBy 是 NOP，TSQL 将(大致):

This is fine, but if the same user updates it twice in a row, the UpdatedBy is a NOP, and the TSQL will be (roughly):

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

就我而言，问题在于当前所有表上都有一个带大括号的审计触发器，它检查审计列是否已更新，如果没有则假定开发人员有错(替换 SUSER_SNAME()，尽管它也很容易抛出错误).

In my case, the problem is that there is currently a belt-and-braces audit trigger on all tables, which checks to see if the audit column has been updated, and if not assumes the developer is at fault (substituting SUSER_SNAME(), although it could just as readily throw an error).

我真正希望能够做的是说始终更新此列，即使它不脏" - 这可能吗?

What I'd really like to be able to do is say "always update this column, even if it isn't dirty" - is this possible?

推荐答案

基于 KristoferA 的回答，我在下面得到了like；这是邪恶而脆弱的(反射通常是)，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:

Based on KristoferA's answer, I ended up with something like below; this is evil and brittle (reflection often is), but may have to suffice for now. The other side of the battle is to change the triggers to behave:

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);
                }
            }
        }
    }
}

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