Open Winform based on result from SQL Query

Question

I am currently in the process of transferring an Access97 Database Application to a new WinForms application.

We have a central form for all "Accounts" which shows the general account data, within that form there is a button that opens another form, the application gets the form name from a SQL query using an example of the table below.

| ClientID | FormName |
+----------+----------+
|    1     |   frm1   |
|    2     |   frm2   |

So if the ClientID is 1 then the button should open Form1 if the ClientID is 2 the button should open Form2.

My question is how would I get WinForms to run the query on the button click to then open the corresponding form found within the table?

Any help is much appreciated.

Answer 1

You will need to write an SQL helper method. Something like the following (which I have not checked and hacked up)

public static T SQLGet<T>(SqlConnection conn, string sql)
{
    using (SqlCommand command = new SqlCommand())
    {
        command.Connection = conn;
        command.CommandTimeout = 0; // No timeout - set or remove.
        command.CommandText = sql;
        return (T)Convert.ChangeType(Command.ExecuteScalar(), typeof(T));
    }
}

you can use this like

SqlConnection conn = new SqlConnection(someValidConnectionString);
string formName = Utilities.SQLGet<string>(conn, 
    "SELECT [FormName] " + 
    "FROM [SomeTable] WHERE [ClientID] = 1;") // Not considering SQL injection here!

Now you can use reflection with the retrieved name formName

Type t = assembly.GetType(formName);
Form frm1 = (Form)Activator.CreateInstance(t);

I hope this helps.

Note. this does not have error handling.