Question

Currently having an issue with this test windows form application. The constructor works to add data to a datagridview. However, when I click the button, it fails to add anything to run the sql command with the error ExecuteNonQuery: Connection property has not been initialized. Below is my code. I have found questions with similar issues but they do not address this issue with calling the database at multiple points in the code.

namespace TestApplication
{
public partial class Form1 : Form
{
    public SqlDatabase db;
    string myConnectionString = ConfigurationManager.ConnectionStrings["DF06Data_Tools"].ToString();
    public Form1()
    {
        InitializeComponent();
        db = new SqlDatabase(myConnectionString);
        UpdateGrid();

    }

    private void Form1_Load(object sender, EventArgs e)
    {

    }

    public void UpdateGrid()
    {
        string sql = "SELECT *  FROM [Data_Tools].[dbo].[TestTable]";
        DbCommand cmd = db.GetSqlStringCommand(sql);
        DataSet TableDataSet = db.ExecuteDataSet(cmd);
        dataGridView1.DataSource = TableDataSet.Tables[0];
        cmd.Dispose();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        string sql = "INSERT INTO [Data_Tools].[dbo].[TESTTABLE] (name, id) VALUES('bob', '8')";
        DbCommand cmd = db.GetSqlStringCommand(sql);
        cmd.ExecuteNonQuery();
        UpdateGrid();
    }
}
}

Answer 1

You need to open your connection before calling ExecuteNonQuery. The call in your constructor opens the connection, issues the command, and then closes the connection for you.

From MSDN:

The call to ExecuteDataSet opens a connection, populates a DataSet,
and closes the connection before returning the result.

Also from MSDN:

private static void CreateCommand(string queryString,
    string connectionString)
{
    using (SqlConnection connection = new SqlConnection(
               connectionString))
    {
        SqlCommand command = new SqlCommand(queryString, connection);
        command.Connection.Open();
        command.ExecuteNonQuery();
    }
}