How to add in a sql query a condition that checks if ckeckboxe are checked?

I have several comboboxes and I would like to check those that are checked to retrieve their values ​​and use them in a sql query.

I tried to put all the checkboxes in a flowLayoutPanel and use a foreach to retrieve their contents.I think it’s a syntax problem in my sql query.

 List<string> selection = new List<string>();
            foreach (CheckBox cb in flowLayoutPanel1.Controls)
            {
                if (cb.Checked)
                    selection.Add(cb.Text);
            }

 SqlCommand command = new SqlCommand("SELECT JOB_HEADER.P FROM JOB_HEADER WHERE JOB_HEADER.MODE_F = selection")

Here is the mistake I get : An unhandled exception of type ‘System.Data.SqlClient.SqlException’ occurred in System.Data.dll

Additional information: Invalid column name ‘selection’.

Sorry if the solution is obvious I am a beginner. Thanks for your help.

Answer

Your actual error is caused by the word selection. This is not the list variable but a literal text inside a string and the database engine has no way to know how to extract the list values from that word. So it thinks that you have written a column name and it cannot find it.

The solution is more complex than you think.

You need a collection of parameters and a collection of names to put inside an IN clause

int pcount = 1;

// This is where we keep the placeholder text for the parameters 
List<string> names = new List<string>();

// This is the list of parameters built using the checkboxes checked state
List<SqlParameter> prms = new List<SqlParameter>();

foreach (CheckBox cb in flowLayoutPanel1.Controls)
{
    if (cb.Checked)
    {
        names.Add("@p" + pcount);
        prms.Add(new SqlParameter 
        {
            ParameterName = "@p" + pcount, 
            SqlDbType = SqlDbType.NVarChar, 
            Value = cb.Text,
            // For performance it would be useful also to specify the column size
            // Size = 100,
        });
        pcount++;
    }
}

// Build the sql command adding all the parameters placeholders inside an IN clause
string cmdText = @"SELECT JOB_HEADER.P FROM JOB_HEADER WHERE JOB_HEADER.MODE_F IN(";
cmdText += string.Join(",", names) + ")";

SqlCommand command = new SqlCommand(cmdText, connection);
// Give the parameters collection to the command
command.Parameters.AddRange(prms.ToArray());