Delete from Database advice

Question

I am trying to create a C# delete function. This is what I have so far, although I want to adapt it to work like my pseudo code below.

Pseudo code for new function

//public bool delete(Dictionary <string, string> id, string tableName)
//{

//reader or another object

//open conenction 

//statement takes input of the primary key of the row to be edited
//as an array of one, the value plus the name of the column representing the primary key
//for the row to be deleted, as well as the table name 


//connection

//excute 

//return bool? 

//}
//}

What I've tried:

public bool Delete(Dictionary <string, string> id, string tableName)
{            
    //reader or another object            

    //open connection 
    using (SqlConnection conn = new SqlConnection(ConnectionString))
    {    
        conn.Open();
        using (SqlCommand cmd = new SqlCommand("DELETE FROM tableName WHERE id=id", conn))
        {
            cmd.ExecuteNonQuery();
        }              
    }
}

But when doing this I am struggling with adapting the code and would appreciate some help please. I can provide more info if needed. I want the new function to take the input of the unique identifier of the row to be edited as an array of one – the value plus the name of the column representing the primary key - for the row to be deleted, as well as the table name.

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the [How to Ask](https://stackoverflow.com/help/how-to-ask) page for help clarifying this question. — Albireo, Dec 17 '15 at 14:49
Okay so the problem i am encountering is how to adjust my current code to fit the new purpose, the part i am struggling with is the statement. — blueboy123, Dec 17 '15 at 14:54
Possible duplicate of [sqlcommand execute query not updating deleting and inserting](http://stackoverflow.com/questions/11344528/sqlcommand-execute-query-not-updating-deleting-and-inserting) — blas3nik, Dec 17 '15 at 14:56
All of your questions that I've seen so far are basic syntax questions. Have you read the supporting documentation? [MSDN](https://msdn.microsoft.com/en-us/library/ms233823.aspx) is pretty useful once you get used to reading it. Questions about syntax which can easily be solved via a simple Google search are generally poorly received here, especially as there are many duplicates even here on this site. — Michael McGriff, Dec 17 '15 at 15:23
Hi Michael thanks for your help, okay I will look at that now, although I think that these functions are slightly harder then the basic. — blueboy123, Dec 17 '15 at 15:57

score 2 · Answer 1 · answered Dec 17 '15 at 14:55

2

You need to take the values from your arguments and put them into a correctly formatted sql string, like so:

public bool Delete(string id, string column, string table)
{
  using (SqlConnection conn = new SqlConnection(ConnectionString))
  {
     conn.Open();
     var query = String.Format("DELETE FROM {0} WHERE {1}='{2}'", table,column, id)
     using (SqlCommand cmd = new SqlCommand(query))
     {
          cmd.ExecuteNonQuery();
     }
  }
}

This approach has many performance and security issues, but I take it you are doing this for educational purposes?

answered Dec 17 '15 at 14:55

Mikael Nitell

1,069
6
16

Okay i will give that a go, yep i don't mind about that at this stage. It says not all code paths are returning a value so how would i return a boll en at the end to say that delete has worked? – blueboy123 Dec 17 '15 at 15:13
Yeah, that makes sense, or make the method void for now. – Mikael Nitell Dec 17 '15 at 15:33
The thing is i have to do it with public bool Delete(Dictionary id, string tableName) so I can't use that method but thanks for your help – blueboy123 Dec 17 '15 at 16:38

Delete from Database advice

1 Answers1