Dapper - return GUID generated by SQL Server - dapper

Question

All of the Dapper posts on S/O related to returning a value after insert seem to relate only to the Identity value. I have tried to apply the logic in those answers to my issue, but it's not working.
I want to return a GUID generated by SQL Server which is not an Identity field. This is my code:
public bool Insert(Record record)
{
SqlConnection connection = new SqlConnection(_configuration.GetConnectionString("Production"));
connection.Open();
using (connection)
{
string query = "DECLARE #RSGUID uniqueidentifier SET #RSGUID = NEWID(); INSERT INTO [dbo].[Table] ([Result], [ResultSetKey]) VALUES (#Result, #RSGUID); SELECT #RSGUID";
// it's this next line that I'm confused on:
var resultSetKey = connection.Query<string>(query, #RSGUID).Single();
return connection.Execute(query, record) > 0;
}
}
I know the var resultsSetKey line is not correct, and this is what I need help with. How can I get the GUID generated by SQL Server into a variable?

Answer 1

I can't test right now, but this should work:
public bool Insert(Record record)
{
using (var connection = new SqlConnection(_configuration.GetConnectionString("Production"))
{
string query = "DECLARE #RSGUID uniqueidentifier; SET #RSGUID = NEWID(); INSERT INTO [dbo].[Table] ([Result], [ResultSetKey]) VALUES (#Result, #RSGUID); SELECT #RSGUID";
var resultSetKey = connection.ExecuteScalar<string>(query).SingleOrDefault();
return !String.IsNullOrEmpty(resultSetKey);
}
}
You can get a kickstart with Dapper following the tutorial here:
https://medium.com/dapper-net/get-started-with-dapper-net-591592c335aa
but honestly it's really not clear what you are trying to do. What is the #Result variable that you are using in the T-SQL code?

Answer 2

A very old question, I know - but I've just had exactly the same issue here and found a working solution, so I'm sure somebody else will in benefit from this late answer in the future.
The following works as desired. The key for me was understanding the datatype to use in C# to contain the returned stream_id value, which is System.Guid, not string. Though of course you may wish to convert it to a string to display it to a user for example as plain text.
My stored procedure for entering a new file into the filetable is
USE [dbname]
GO
/****** Object: StoredProcedure [dbo].[newFile] Script Date: 28/11/2022 14:34:50 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [dbo].[newFile]
#fileBinary varbinary(max) = 0,
#fileName varchar(256) = 0
AS
BEGIN
SET NOCOUNT ON;
DECLARE #newFileId table (stream_id uniqueidentifier);
INSERT INTO dbo.files (file_stream, name) OUTPUT INSERTED.[stream_id] into #newFileId
VALUES (#fileBinary, #fileName);
SELECT * FROM #newFileId
END
And here is the method to add said new file programmatically (I'm fully aware this example includes no error handling etc)
public class fileAccess
{
public System.Guid newFileId;
public void uploadNewFile(byte[] newFileBinary, string newFileName)
{
var procedure = "[newFile]";
var parameters = new
{
fileBinary = newFileBinary,
fileName = newFileName,
};
using (DbConnection connection = new Microsoft.Data.SqlClient.SqlConnection(helper.cnnVal("dbname")))
{
newFileId = connection.ExecuteScalar<System.Guid>(procedure, parameters, commandType: CommandType.StoredProcedure);
}
}
}
Called here (a test example, uploading a file by clicking a button, which pulls a file from my desktop)
private void button6_Click(object sender, EventArgs e)
{
fileAccess db = new fileAccess();
byte[] fileBinary = File.ReadAllBytes(#"C:\Users\username\Desktop\test.docx");
db.uploadNewFile(fileBinary, "test.docx");
string message = "New file succesfully uploaded. File ID: " + Convert.ToString(db.newFileId);
string caption = "Success.";
MessageBox.Show(message, caption, MessageBoxButtons.OK);
}