导致此错误的原因：类型'System.String'不支持序列运算符

Question

Here is my code:

    IEnumerable<DataAccessLayer.SQLPendingEventRecord> dataset1 = _v3Context.SQLPendingEvents
                     .Where(sp => sp.EventType.ToString() == str100w && sp.EventDateTime > dtStartDate && !sp.KeyDeviceID.ToString().Contains('~'))
                     .AsEnumerable() // further processing occurs on client
                     .Select((sp, index) => new DataAccessLayer.SQLPendingEventRecord
                     {
                         ID = index + 1,
                         KeyDeviceID=sp.KeyDeviceID,
                         UpdateTime=sp.UpdateTime,
                         EventClass=sp.EventClass,
                         EventCode=sp.EventCode,
                         EventType=sp.EventType,
                         EventDateTime=Convert.ToDateTime(sp.EventDateTime),
                         KeyPropertyID=Convert.ToInt32 (sp.KeyPropertyID),
                         KeyEntityID=Convert.ToInt32 (sp.KeyEntityID),
                         EventText=sp.EventText,
                         KeyUserID=sp.KeyUserID,
                         //sp.EventImage,
                         TaskType=sp.TaskType,
                         TaskSubType=sp.TaskSubType,
                         UniqueTaskID=sp.UniqueTaskID
                     }).ToList();

I have just added: && !sp.KeyDeviceID.ToString().Contains('~')) Now, I get odd error msg: Sequence operators not supported for type 'System.String'. Before that, I had no problem. Now, I get this cryptic error message. I need to put this all in one query, due to the size of the database. Any ideas?

Answer 1

I suspect the problem is that it's using Enumerable.Contains(string, char) (because string implements IEnumerable<char> ) whereas you really want string.Contains(string) .

Just changing it to:

!sp.KeyDeviceID.ToString().Contains("~")

may fix the issue.

Note that if KeyDeviceID is already a string property, I'd get rid of the ToString() call:

!sp.KeyDeviceID.Contains("~")

Answer 2

Are you using Linq to SQL? Linq to SQL does not support all of the .Net functionality for data types. You can use SQLFunctions to replicate some of the functionality. If sp.KeyDeviceID is not a string, then using ToString() would throw an error if you are using Linq to SQL. Try

IEnumerable<DataAccessLayer.SQLPendingEventRecord> dataset1 = _v3Context.SQLPendingEvents
                     .Where(sp => sp.EventType.ToString() == str100w && sp.EventDateTime > dtStartDate && !**SQLFunctions.CharIndex(sp.KeyDeviceID,"~")>0)**
                     .AsEnumerable() // further processing occurs on client
                     .Select((sp, index) => new DataAccessLayer.SQLPendingEventRecord
                     {
                         ID = index + 1,
                         KeyDeviceID=sp.KeyDeviceID,
                         UpdateTime=sp.UpdateTime,
                         EventClass=sp.EventClass,
                         EventCode=sp.EventCode,
                         EventType=sp.EventType,
                         EventDateTime=Convert.ToDateTime(sp.EventDateTime),
                         KeyPropertyID=Convert.ToInt32 (sp.KeyPropertyID),
                         KeyEntityID=Convert.ToInt32 (sp.KeyEntityID),
                         EventText=sp.EventText,
                         KeyUserID=sp.KeyUserID,
                         //sp.EventImage,
                         TaskType=sp.TaskType,
                         TaskSubType=sp.TaskSubType,
                         UniqueTaskID=sp.UniqueTaskID
                     }).ToList();