Question

I’ve configured a db w/ a FileStream group and have a table w/ File type on it. When attempting to insert a streamed file and after I create the table row, my query to read the filepath out and the buffer returns a null file path. I can’t seem to figure out why though. Here is the table creation script:

    /****** Object:  Table [dbo].[JobInstanceFile]    Script Date: 03/22/2010 18:05:36 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

SET ANSI_PADDING ON
GO

CREATE TABLE [dbo].[JobInstanceFile](
    [JobInstanceFileId] [int] IDENTITY(1,1) NOT NULL,
    [JobInstanceId] [int] NOT NULL,
    [File] [varbinary](max) FILESTREAM  NULL,
    [FileId] [uniqueidentifier] ROWGUIDCOL  NOT NULL,
    [Created] [datetime] NOT NULL,
 CONSTRAINT [PK_JobInstanceFile] PRIMARY KEY CLUSTERED 
(
    [JobInstanceFileId] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY] FILESTREAM_ON [JobInstanceFilesGroup],
UNIQUE NONCLUSTERED 
(
    [FileId] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY] FILESTREAM_ON [JobInstanceFilesGroup]

GO

SET ANSI_PADDING OFF
GO

ALTER TABLE [dbo].[JobInstanceFile] ADD  DEFAULT (newid()) FOR [FileId]
GO

Here’s my proc I call to create the row before streaming the file:

    /****** Object:  StoredProcedure [dbo].[JobInstanceFileCreate]    Script Date: 03/22/2010 18:06:23 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

create proc [dbo].[JobInstanceFileCreate]

    @JobInstanceId int,
    @Created datetime

    as

    insert into JobInstanceFile (JobInstanceId, FileId, Created)
    values (@JobInstanceId, newid(), @Created)

    select scope_identity()
GO

And lastly, here’s the code I’m using:

    public int CreateJobInstanceFile(int jobInstanceId, string filePath)
        {
            using (var connection = new SqlConnection(ConfigurationManager.ConnectionStrings["ConsumerMarketingStoreFiles"].ConnectionString))
            using (var fileStream = new FileStream(filePath, FileMode.Open))
            {
                connection.Open();

                var tran = connection.BeginTransaction(IsolationLevel.ReadCommitted);

                try 
                {
                    //create the JobInstanceFile instance
                    var command = new SqlCommand("JobInstanceFileCreate", connection) { Transaction = tran };
                    command.CommandType = CommandType.StoredProcedure;
                    command.Parameters.AddWithValue("@JobInstanceId", jobInstanceId);
                    command.Parameters.AddWithValue("@Created", DateTime.Now);

                    int jobInstanceFileId = Convert.ToInt32(command.ExecuteScalar());

                    //read out the filestream transaction context to stream the file for storage
                    command.CommandText = "select [File].PathName(), GET_FILESTREAM_TRANSACTION_CONTEXT() from JobInstanceFile where JobInstanceFileId = @JobInstanceFileId";
                    command.CommandType = CommandType.Text;
                    command.Parameters.AddWithValue("@JobInstanceFileId", jobInstanceFileId);

                    using (SqlDataReader dr = command.ExecuteReader())
                    {
                        dr.Read();

                        //get the file path we're writing out to
                        string writePath = dr.GetString(0);

                        using (var writeStream = new SqlFileStream(writePath, (byte[])dr.GetValue(1), FileAccess.ReadWrite))
                        {
                            //copy from one stream to another
                            byte[] bytes = new byte[65536];
                            int numBytes;
                            while ((numBytes = fileStream.Read(bytes, 0, 65536)) > 0)
                                writeStream.Write(bytes, 0, numBytes);
                        }
                    }

                    tran.Commit();

                    return jobInstanceFileId;
                }
                catch (Exception e)
                {
                    tran.Rollback();
                    throw e;
                }
            }
        }

Can someone please let me know what I’m doing wrong. In the code, the following expression is returning null for the file path and shouldn’t be:

//get the file path we’re writing out to
string writePath = dr.GetString(0);

The server is different then the computer the code is running on but the necessary shares appear to be in order and I have also run the following:

EXEC sp_configure filestream_access_level, 2

Any help would be greatly appreciated. Thanks!

Answer 1

You cannot open SqlFileStream on a NULL value. Change the INSERT statement to set File = 0x and it should start working.

PS.
Some performance considerations:

1. You can avoid the additional round-trip to the server by issuing an INSERT with OUTPUT clause that returns transaction context and file path of the newly inserted blob.
2. If you don’t intend to read from SqlFileStream, open it for Write only. In this particular case this may not be a big deal, because the file you’re opening is empty. But if you’re updating a large file, opening it for ReadWrite will have Sql copy the whole file first, and only then let you play with it.