This is a part of a series of blog posts on data access with Dapper. To see the full list of posts, visit the Dapper Series Index Page. I want to focus specifically on the Dapper bits here but validation is really important. In a real-world scenario, you should be validating any data that is passed in to the server. I recommend using Fluent Validation. Inserting a single new record is really easy. The version of the ExecuteAsync method we used here accepts two parameters: a string containing the SQL statement to execute and an object containing the parameter values to bind to the statement.
In this case, it is an instance of the Aircraft class which has properties with names matching the parameters defined in the INSERT statement. That means the primary key is generated by the database when the row is inserted.
We will likely need to pass that value back to whoever called the API so they know how to retrieve the newly inserted Aircraft. Updating an existing entity is similar to inserting. Again, the parameters in the SQL statement match the names of the properties in our Aircraft class.
Deleting an entity is the easiest of the three operations since it only requires a single parameter: the unique Id to identify the entity being deleted.
To execute the delete, call the ExecuteAsync method passing in the SQL statement and an anonymous object containing the Id to delete. I really appreciate how simple delete is using Dapper. When using Entity Framework, delete requires you to first fetch the existing entity, then delete it.
That requires 2 round trips to the database while the approach we used here only requires a single round trip. Basic insert, update and delete operations are easy to implement using Dapper. Real world scenarios are often a little more complex and we will dig into some of those scenarios in future posts:. Insert Inserting a single new record is really easy. Wrapping it up Basic insert, update and delete operations are easy to implement using Dapper. Real world scenarios are often a little more complex and we will dig into some of those scenarios in future posts: Bulk inserts, updates and deletes Managing transactions Optimistic concurrency checks.
Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. If you step through the results, you can see that the proper return values are coming down in the retResults value, but I am not able to access the values the way it is described in the documentation as below. I suspect untested that this is purely a mismatch in how you name the parameter; try note the removed :.
The caveats on this are that you must specify an entry for every property in the class you are using, even if those properties do not exist in the target table, as a parameter for the stored procedure. This can be annoying if you have a number of fields which are view fields in MVC situations. To get the return value, you just have to use Execute, and make sure your last statement is Select Identity in the stored procedure.
PS: I hate using Dapper's DynamicParameters or any other device that requires you to use a different insert or update method for each of your classes in a generic repository. I ran into a similar problem reading the results of a QueryMultiple. The first call to Read returned the correct type, the second returned a DapperRow. I found that using the typed version of Read :. I've pared this down for simplicity. I'm using output parameters because that gives me full control of the datatype that is passed back.
I could use this approach with any other scenario, not just inserts. The DynamicParameters solution is not clean to me. Learn more. Return Values from Dapper. Asked 7 years, 3 months ago.
Active 2 months ago. Viewed 29k times. I am trying to call a stored procedure using Dapper.
Dapper - Stored Procedure
Net and get return values. Int32, direction: ParameterDirection. Add " b", dbType: DbType. Output ; p. Add " c", dbType: DbType. ReturnValue ; cnn. Execute "spMagicProc", p, commandType: commandType. Mykola 3, 6 6 gold badges 19 19 silver badges 38 38 bronze badges. SingleOrDefault ;? DJ Kraze, I edited my question to refer to the documentation, thanks!
I am trying this same thing and am receiving a "Specified cast is not valid. I am declaring my Parameter as DbType.I'm struggling with how to properly map output parameters back to an object using Dapper, when I create DynamicParamters from a template object. My hope was that the above code would map the resulting ID back into the entity that I created the parameters from in the first place.
No matter what I try I am unable to get the parameter to return from the stored procedure. Calling parameters. What is the correct way to get an output parameter back from Dapper when trying to use an object template for my DynamicParameters? Figured this out, didn't properly update my code when I moved from template to parameters. I was passing entity into my query, not parameters.
Once I replaced that I could even get rid of the explicit addition of the Id output parameter. This is much nicer! Returning Output Parameters with Dapper for. NET Core. Question I'm struggling with how to properly map output parameters back to an object using Dapper, when I create DynamicParamters from a template object.
Add " Id", dbType: DbType. Int32, direction: ParameterDirection. Output ; parameters. Id ; await conn. StoredProcedure ; My hope was that the above code would map the resulting ID back into the entity that I created the parameters from in the first place. Bulk Delete. Bulk Update.
Bulk Merge.Learn about Microsoft technologies. So for this purpose we need to take return value from stored procedure which is either string or integer or anything as per application requirement. Since ABC housing society is very big it's difficult to manage complaints manually of their flat customers, so they decided to build the sample application which covers the following scenario. User can raise the complaint type and short description using Text boxes.
The unique ComplaintId need to be generated instantly after raising the complaint to track status.C# Dapper For Beginners Using Stored Procedures Insert Query Part 8
The ComplaintId should be the combination of first four characters of complaint type text and Database auto generated number. So based on preceding scenario let's start building application step by step so beginners can also understand.
Now let us start with a step by step approach from the creation of a simple MVC application as in the following: " Start ", then "A ll Programs" and select "Microsoft Visual Studio ". After clicking, the following window will appear:. Step 3: Create Model Class. Now let's create the model class named ComplaintModel. Note: It is not mandatory that Model class should be in Model folder, it is just for better readability you can create this class anywhere in the solution explorer.
This can be done by creating different folder name or without folder name or in a separate class library. Step 5 : Create Table and Stored procedure. Now before creating the views let us create the table name ComplaintDetails in database according to store the complaint details:.
I hope you have created the same table structure as shown above. ConnectionStrings[ "SqlConn" ]. Add " ComplaintType"Obj.
Basic Insert Update and Delete with Dapper
ComplaintType ; ObjParm. Add " ComplaintDesc"Obj. ComplaintDesc ; ObjParm. Output,size ; connection ; con. Open ; con. Now click on Add Complaint button without entering the details then the following error message shows which we have defined in model class as.
Since this is a demo, it might not be using proper standards, so improve it depending on your skills. Configure the database connection in the web. Summary I hope this article is useful for all readers. If you have any suggestions please contact me. Read more articles on ASP.
Post a Comment. Back To Top.The ExecuteAsync can execute a command one or multiple times asynchronously and return the number of affected rows. Try it:. NET Core. NET Framework. The QueryFirstOrDefaultAsync can execute a query and map asynchronously the first result, or a default value if the sequence contains no elements. The QuerySingleAsync can execute a query and map asynchronously the first result and throws an exception if there is not exactly one element in the sequence.
The QuerySingleOrDefaultAsync can execute a query and map asynchronously the first result, or a default value if the sequence is empty; this method throws an exception if there is more than one element in the sequence. The QuerySingleOrDefaultAsync can execute multiple queries within the same command and map results asynchronously.
Dapper Getting Started Introduction. Async Buffered Transaction Stored Procedure. Bulk Delete. Bulk Update. Bulk Merge. Result; Console. ToList ; FiddleHelper. ToList ; Console. WriteLine orderDetails. Count ; FiddleHelper.
Result; FiddleHelper. QueryMultipleAsync sql. WriteTable orders ; FiddleHelper. Prime Library.I want to insert a bunch of records, and return the inserted records alongside the auto-incremented id. Using Dapper to run this query on a list of players and serialise back into a list of players with the ids I thought I could do this:.
I believe that Query may not support lists of parameters, so I tried connection. Execute instead. Execute works, but obviously it doesn't return back the inserted players with their Ids. So building an ExpandoObject with properties from my Players and then passing that into Dapper Query. It works, but it seems pretty dirty.
Any suggestions on how to improve this? Dapper just unrolls it for you unless it is a very specific async scenario where it can pipeline the commands. Dapper does support list-parameter expansion, but this is for leaf-level values, and was constructed for in Your expected usage is one that has been suggested and discussed quite a bit recently; at the current time it isn't supported - the loop unrolling only works for Executehowever, it is looking increasingly likely that we will add something here.
The tricky bit is in deciding what the correct behavior is, and whether it is expected that this would essentially concatenate the results of multiple separate operations. Question I've just started using Dapper and I've run into the following problem. Append string. Bulk Delete. Bulk Update. Bulk Merge.
Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I want to perform this simple test to see whether a table exists. I thought it would be easy just to return an int value depending on whether the table exists. Then you can use ExecuteScalar and it will return 1 if the table exists. Please note that I also corrected your parameters in the SQL statements. They must not be delimited by '.
Instead of using IF. ELSE statement you can use the following query and check whether the result is greater than zero. All above answers are correct and make sense. But you should create a stored procedure that does this check. That way you will have less chance to have syntax errors and way easier to fix. I recommend that the procedure accepts schema name and table name as parameters.
Then select 0 or select 1 depending if found table or not. Dapper can execute procedures, no prob. As others already stated, you are getting error becase your SQL query contains error. Try running it directly in SQL and you will se the same error. If your values suppose to show number of tables you are returning, then Karthik AMR solution seems the best one. If values 1 and 0 is not really a count of how many tables exists, but also could be some chars, then this could also work:.
Learn more. Dapper return single value Ask Question. Asked 3 years, 10 months ago. Active 3 years, 10 months ago. Viewed 6k times. It's something really noddy Callum Linington Callum Linington