Question

I have started today to learn about the SQL connection in C# programming. And I tried some basic thing like the Insert, Delete etc.

And I wanted to try the same thing in another project but I have a problem. Because It shows me an error that I can’t solve 🙁

Error:

A field initializer cannot reference the non-static field, method, or property ‘Artikujt.Form1.con’.

Here is my code (I just started to connect it with the Database in SQL)

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace Artikujt
{
    public partial class Form1 : Form
    {
        SqlConnection con = new SqlConnection(@"Data Source=TALY-PC;Initial Catalog=Katalogi;Integrated Security=True;Pooling=False");
        SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM tblArtikujt", con);
        DataSet dsl = new DataSet();    

        public Form1()
        {
            InitializeComponent();
        }    
    }
}

The error is in this code at the variable con

SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM tblArtikujt", con);

I created the Database in SQL (in Visual Studio)… I also added the Data Source. I did the exact thing that I did before…. but it isn’t working 🙁

Answer 1

The error is exactly what it says. You cannot use con in your initialization of da because it will only be created during an instance creation. You will need to create con as static or put your initialization lines in your constructor.

HOWEVER, you should probably not do this in practice as you are just asking for somebody to open a SqlConnection and leave it open. You should probably fall more into the practice of creating your connections using a using block to take advantage of the disposing pattern

Static:

public partial class Form1 : Form
{
    static SqlConnection con = new SqlConnection(@"Data Source=TALY-PC;Initial Catalog=Katalogi;Integrated Security=True;Pooling=False");
    SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM tblArtikujt", con);
    DataSet dsl = new DataSet();    


    public Form1()
    {
        InitializeComponent();
    }

Or instantiation in the constructor:

public partial class Form1 : Form
{
    SqlConnection con;
    SqlDataAdapter da;
    DataSet dsl;  

    public Form1()
    {
        InitializeComponent();
        con = new SqlConnection(@"Data Source=TALY-PC;Initial Catalog=Katalogi;Integrated Security=True;Pooling=False");
        da = new SqlDataAdapter("SELECT * FROM tblArtikujt", con);
        dsl = new DataSet();  
    }
}

I will let you research the using block yourself