No exception, but my data isn't written into the SQL Server database

Question

I'm stuck at a loose end with inserting a new data entry into a SQL Server database. I have all the info I want to store in the following class:

public class NewSearchQuery //object reference q
{
    public string Name, Location, SearchType, Path, Method;
    public int RefNum;
    public double Fee;
    public bool Paid;
}

and after the user has filled in the form etc.. this is my code to save the info to the database:

        bool complete;
        string sql = $"Insert into PrivateLog (Id,Applicant,ApplicationDate,Location,Search,Paid,Method,Amount,Files) values({q.RefNum}, '{q.Name}', {AppDate}, '{q.Location}', '{q.SearchType}', {q.Paid}, '{q.Method}', {q.Fee}, '{q.Path}')";
        cnn.Open();
        try
        {
            SqlDataAdapter adapter = new SqlDataAdapter();
            SqlCommand command = new SqlCommand(sql, cnn); //The Connection String cnn is in a public string variable above this method. 
            adapter.InsertCommand = new SqlCommand(sql, cnn);
            command.Dispose();
            complete = true;
        }
        catch (System.Exception e)
        {
            complete = false;
        }
        cnn.Close();
        return complete;

Here is what my table designer looks like:

Can anyone show me why the new data entry might not be going through?

Answer 1

You don't need an SqlDataAdapter in that case, you can simply execute your command:

try
{
    SqlCommand command = new SqlCommand(sql, cnn);
    command.ExecuteNonQuery();
    complete = true;
}

Although I recommend using command.Parameters to add your parameters values, protecting a possible SQL injection:

bool complete;
string sql = "Insert into PrivateLog (Id, Applicant, ApplicationDate, Location, Search, Paid, Method, Amount, Files) values(@RefNum, @Name, @AppDate, @Location, @SearchType, @Paid, @Method, @Fee, @Path)";
cnn.Open();
try
{
    SqlCommand command = new SqlCommand(sql, cnn);

    command.Parameters.Add("@RefNum", SqlDbType.Int).Value = q.RefNum;
    command.Parameters.Add("@Name", SqlDbType.VarChar).Value = q.Name;
    command.Parameters.Add("@AppDate", SqlDbType.DateTime).Value = AppDate;
    command.Parameters.Add("@Location", SqlDbType.VarChar).Value = q.Location;
    command.Parameters.Add("@SearchType", SqlDbType.VarChar).Value = q.SearchType;
    command.Parameters.Add("@Paid", SqlDbType.Bit).Value = q.Paid;
    command.Parameters.Add("@Method", SqlDbType.VarChar).Value = q.Method;
    command.Parameters.Add("@Fee", SqlDbType.Decimal).Value = q.Fee;
    command.Parameters.Add("@Path", SqlDbType.VarChar).Value = q.Path;

    command.ExecuteNonQuery();
    command.Dispose();
    complete = true;
}
catch (System.Exception e)
{
    complete = false;
}
cnn.Close();
return complete;