Calling a Stored Procedure with a Parameter in C# using ExecuteNonQuery()

Background

I had a very frustrating issue the other day. I was trying to call a Stored Procedure (SP) from my C# code using the same command I use to call the SP in MySQL. I kept getting a very irritating error:

Exception error: “MySql.Data.MySqlClient.MySqlException: Parameter ‘@_itemId’ must be defined”

My SP call required me to pass a parameter (@_itemId) that it would handle. This was not a parameter I needed to set in my code - I just simply needed to add it as part of my SP call.

My Code

I was trying to keep my code simple - build the SQL statement with incoming JSON using a foreach loop, append the id and connection string, and make the call to the SP. I think in total, I have about 10 lines of actual code that are actually doing something, as opposed to lines of comments or log lines. So why didn't this work??

MySqlCommand cmdSQL = new MySqlCommand($@"{spCallStatement}", conn);
cmdSQL.ExecuteNonQuery();

Troubleshooting

I spent a good bit of time troubleshooting. I tried to create a variable and add the parameter to the call. I tried several other methods besides ExecuteNonQuery(). I logged my spCallStatement text, copied and pasted it into MySQL, and it ran fine but it would NOT run from my code. I added a lot of log lines to determine that it was making the connections but it was definitely failing when making the SP call. Frustrating!!

myConnectionString

After honing in on my Google-Fu skills, I finally put the pieces together and realized it wasn't the method I was using. It wasn't my code, per se, it was my connection string. I needed to add a setting to my connection string. I didn't share my connection string above, for obvious reasons, but it essentially gathers the necessary components to connect to the db. All I had to do was append "Allow User Variables=True" to the end of my connection string.

myConnectionString += $"{myConnectionString}Allow User Variables=True";

Success!!

That was it. The simple setting was all I had to add and now my code is running as expected. It's a beautiful thing when your code finally works as you expect it, isn't it?  ;) 

Why a Stored Proc?

Let the SP do the work to see if the record exists in your table to determine whether you should perform an update/insert/etc of the record. Make one call from your program/code to your database instead of multiple.