C# 实体框架保存更改错误详细信息

在数据上下文中使用

SaveChanges

保存更改时，是否有方法确定哪个实体导致错误？例如，有时我会忘记将日期分配给不可为空的日期字段，并出现“无效日期范围”错误，但我没有得到关于哪个实体或哪个字段导致该错误的信息（我通常可以通过仔细查看所有对象来跟踪它，但这非常耗时）。堆栈跟踪非常无用，因为它只向我显示

SaveChanges

调用中的一个错误，而没有任何关于它到底发生在哪里的附加信息

请注意，我现在不想解决任何特定的问题，我只想知道是否有办法判断哪个实体/字段导致了问题

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以堆栈跟踪的快速示例为例—在本例中，由于未在

IAComment

实体上设置

CreatedOn

date，因此发生了一个错误，但是无法从该错误/堆栈跟踪中分辨出来

    [SqlTypeException: SqlDateTime overflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM.]
   System.Data.SqlTypes.SqlDateTime.FromTimeSpan(TimeSpan value) +2127345
   System.Data.SqlTypes.SqlDateTime.FromDateTime(DateTime value) +232
   System.Data.SqlClient.MetaType.FromDateTime(DateTime dateTime, Byte cb) +46
   System.Data.SqlClient.TdsParser.WriteValue(Object value, MetaType type, Byte scale, Int32 actualLength, Int32 encodingByteSize, Int32 offset, TdsParserStateObject stateObj) +4997789
   System.Data.SqlClient.TdsParser.TdsExecuteRPC(_SqlRPC[] rpcArray, Int32 timeout, Boolean inSchema, SqlNotificationRequest notificationRequest, TdsParserStateObject stateObj, Boolean isCommandProc) +6248
   System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async) +987
   System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result) +162
   System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method) +32
   System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method) +141
   System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior) +12
   System.Data.Common.DbCommand.ExecuteReader(CommandBehavior behavior) +10
   System.Data.Mapping.Update.Internal.DynamicUpdateCommand.Execute(UpdateTranslator translator, EntityConnection connection, Dictionary`2 identifierValues, List`1 generatedValues) +8084396
   System.Data.Mapping.Update.Internal.UpdateTranslator.Update(IEntityStateManager stateManager, IEntityAdapter adapter) +267

[UpdateException: An error occurred while updating the entries. See the inner exception for details.]
   System.Data.Mapping.Update.Internal.UpdateTranslator.Update(IEntityStateManager stateManager, IEntityAdapter adapter) +389
   System.Data.EntityClient.EntityAdapter.Update(IEntityStateManager entityCache) +163
   System.Data.Objects.ObjectContext.SaveChanges(SaveOptions options) +609
   IADAL.IAController.Save(IAHeader head) in C:\Projects\IA\IADAL\IAController.cs:61
   IA.IAForm.saveForm(Boolean validate) in C:\Projects\IA\IA\IAForm.aspx.cs:198
   IA.IAForm.advance_Click(Object sender, EventArgs e) in C:\Projects\IA\IA\IAForm.aspx.cs:287
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +118
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +112
   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5019

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我认为这是不可能的：您可以使用对象的状态来了解哪些将被保存（保存前）和哪些已被保存（在异常中），但在第二组中，您将无法知道哪一个抛出了异常

西班牙文版本：

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中文：

一个选项是处理，这使您有机会在保存更改之前对实体执行验证，甚至在必要时取消保存。通过这种方式，您可以确保在尝试保存更改之前设置了任何不可为null的属性，并避免依赖异常处理。

我想我可能会单独调用SaveChanges（）。正是因为这个原因，我通常会这么做。我可以问一下为什么一次保存多个实体吗？如果必须的话，我会听从其他人的建议，事先验证实体

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或者，也许有更好的方法来构造代码，以便在有效的实体中甚至不会试图保存。可以分离实体，然后在将它们附加到新上下文之前通过验证方法运行它们。希望有帮助

如果您所需要做的只是查看实际的内部异常，那么您所要做的就是将保存更改放在try块中，捕获异常并查看它

---

我一直这样做，而且效果很好。

以下是我的两个检查示例：datetime=0或字符串溢出：

public partial class MyContext    
{
    private static Dictionary> _fieldMaxLengths;
    partial void OnContextCreated()
    {
        InitializeFieldMaxLength();
        SavingChanges -= BeforeSave;
        SavingChanges += BeforeSave;
    }

    private void BeforeSave(object sender, EventArgs e)
    {
        StringOverflowCheck(sender);
        DateTimeZeroCheck(sender);
        CheckZeroPrimaryKey(sender); 
    }

    private static void CheckZeroPrimaryKey(object sender)
    {
        var db = (CTAdminEntities)sender;
        var modified = db.ObjectStateManager.GetObjectStateEntries(EntityState.Added | EntityState.Modified);
        foreach (var entry in modified.Where(entry => !entry.IsRelationship))
        {
            var entity = (EntityObject)entry.Entity;
            Debug.Assert(entity != null);
            var type = entity.GetType();
            foreach (var prop in type.GetProperties().Where(
                p => new[] { typeof(Int64), typeof(Int32), typeof(Int16) }.Contains(p.PropertyType)))
            {
                var attr = prop.GetCustomAttributes(typeof (EdmScalarPropertyAttribute), false);
                if (attr.Length > 0 && ((EdmScalarPropertyAttribute) attr[0]).EntityKeyProperty)
                {
                    long value = 0;
                    if (prop.PropertyType == typeof(Int64))
                        value = (long) prop.GetValue(entity, null);
                    if (prop.PropertyType == typeof(Int32))
                        value = (int) prop.GetValue(entity, null);
                    if (prop.PropertyType == typeof(Int16))
                        value = (short) prop.GetValue(entity, null);

                    if (value == 0)
                        throw new Exception(string.Format("PK is 0 for Table {0} Key {1}", type, prop.Name));
                    break;
                }
            }
        }
    }

    private static void DateTimeZeroCheck(object sender)
    {
        var db = (CTAdminEntities)sender;
        var modified = db.ObjectStateManager.GetObjectStateEntries(EntityState.Added | EntityState.Modified);
        foreach (var entry in modified.Where(entry => !entry.IsRelationship))
        {
            var entity = (EntityObject)entry.Entity;
            Debug.Assert(entity != null);
            var type = entity.GetType();
            foreach (var prop in type.GetProperties().Where(p => p.PropertyType == typeof(DateTime)))
            {
                var value = (DateTime)prop.GetValue(entity, null);
                if (value == DateTime.MinValue)
                    throw new Exception(string.Format("Datetime2 is 0 Table {0} Column {1}", type, prop.Name));
            }
            foreach (var prop in type.GetProperties().Where(
                    p => p.PropertyType.IsGenericType && 
                    p.PropertyType.GetGenericTypeDefinition() == typeof(Nullable) &&
                    p.PropertyType.GetGenericArguments()[0] == typeof(DateTime)))
            {
                var value = (DateTime?)prop.GetValue(entity, null);
                if (value == DateTime.MinValue)
                    throw new Exception(string.Format("Datetime2 is 0 Table {0} Column {1}", type, prop.Name));
            }
        }
    }

    private static void StringOverflowCheck(object sender)
    {
        var db = (CTAdminEntities)sender;
        var modified = db.ObjectStateManager.GetObjectStateEntries(EntityState.Added | EntityState.Modified);
        foreach (var entry in modified.Where(entry => !entry.IsRelationship))
        {
            var entity = (EntityObject)entry.Entity;
            Debug.Assert(entity != null);
            var type = entity.GetType();
            var fieldMap = _fieldMaxLengths[type.Name];
            foreach (var key in fieldMap.Keys)
            {
                var value = (string)type.GetProperty(key).GetValue(entity, null);
                if (value != null && value.Length > fieldMap[key])
                    throw new Exception(string.Format("String Overflow on Table {0} Column {1}: {2} out of {3}", type, key, value.Length, fieldMap[key]));
            }
        }
    }

    private void InitializeFieldMaxLength()
    {
        if (_fieldMaxLengths != null)
            return;
        _fieldMaxLengths = new Dictionary>();

        var items = MetadataWorkspace.GetItems(DataSpace.CSpace);
        Debug.Assert(items != null);
        var tables = items.Where(m => m.BuiltInTypeKind == BuiltInTypeKind.EntityType);

        foreach (EntityType table in tables)
        {
            var fieldsMap = new Dictionary();
            _fieldMaxLengths[table.Name] = fieldsMap;
            var stringFields = table.Properties.Where(p => p.DeclaringType.Name == table.Name && p.TypeUsage.EdmType.Name == "String");
            foreach (var field in stringFields)
            {
                var value = field.TypeUsage.Facets["MaxLength"].Value;
                if (value is Int32)
                    fieldsMap[field.Name] = Convert.ToInt32(value);
                else
                    // unbounded
                    fieldsMap[field.Name] = Int32.MaxValue;
            }
        }
    }
}