[c#] How to fill DataTable with SQL Table

I am currently creating and reading a DataTable with the following code in my Page_Load

protected void Page_Load(object sender, EventArgs e)
{
    if (Session["AllFeatures1"] == null)
    {
        Session["AllFeatures1"] = GetData();
    }
    table = (DataTable)Session["AllFeatures1"];
    DayPilotCalendar1.DataSource = Session["AllFeatures1"];
    DayPilotNavigator1.DataSource = Session["AllFeatures1"];

    if (!IsPostBack)
    {
        DataBind();
        DayPilotCalendar1.UpdateWithMessage("Welcome!");
    }

    if (User.Identity.Name != "")
    {
        Panel1.Visible = true;
    }
}

I would like to know how to convert this code so that it reads from a SQL query? I am experimenting with the code below but I'm not sure how to connect them so that datatable in my page load fills with the SQL command below.

SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["BarManConnectionString"].ConnectionString);
conn.Open();
string query = "SELECT * FROM [EventOne]";

SqlCommand cmd = new SqlCommand(query, conn);

DataTable t1 = new DataTable();
using (SqlDataAdapter a = new SqlDataAdapter(cmd))
{
    a.Fill(t1);
}

I am stuck at:

table = (DataTable)Session["AllFeatures1"]; 

I would like it to be t1 = (DataTable)Session["AllFeatures1];

The SqlDataReader is a valid data source for the DataTable. As such, all you need to do its this:

public DataTable GetData()
{
    SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["BarManConnectionString"].ConnectionString);
    conn.Open();
    string query = "SELECT * FROM [EventOne]";
    SqlCommand cmd = new SqlCommand(query, conn);

    DataTable dt = new DataTable();
    dt.Load(cmd.ExecuteReader());
    conn.Close();
    return dt;
}

The answers above are correct, but I thought I would expand another answer by offering a way to do the same if you require to pass parameters into the query.

The SqlDataAdapter is quick and simple, but only works if you're filling a table with a static request ie: a simple SELECT without parameters.

Here is my way to do the same, but using a parameter to control the data I require in my table. And I use it to populate a DropDownList.

//populate the Programs dropdownlist according to the student's study year / preference
DropDownList ddlPrograms = (DropDownList)DetailsView1.FindControl("ddlPrograms");
if (ddlPrograms != null)
{
    using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ATCNTV1ConnectionString"].ConnectionString))
    {
        try
        {
            con.Open();
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;
            cmd.CommandText = "SELECT ProgramID, ProgramName FROM tblPrograms WHERE ProgramCatID > 0 AND ProgramStatusID = (CASE WHEN @StudyYearID = 'VPR' THEN 10 ELSE 7 END) AND ProgramID NOT IN (23,112,113) ORDER BY ProgramName";
            cmd.Parameters.Add("@StudyYearID", SqlDbType.Char).Value = "11";
            DataTable wsPrograms = new DataTable();
            wsPrograms.Load(cmd.ExecuteReader());

            //populate the Programs ddl list
            ddlPrograms.DataSource = wsPrograms;
            ddlPrograms.DataTextField = "ProgramName";
            ddlPrograms.DataValueField = "ProgramID";
            ddlPrograms.DataBind();
            ddlPrograms.Items.Insert(0, new ListItem("<Select Program>", "0"));
        }
        catch (Exception ex)
        {
            // Handle the error
        }
    }
}

Enjoy

You can make method which return the datatable of given sql query:

public DataTable GetDataTable()
{
SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["BarManConnectionString"].ConnectionString);
conn.Open();
string query = "SELECT * FROM [EventOne] ";

SqlCommand cmd = new SqlCommand(query, conn);

DataTable t1 = new DataTable();
using (SqlDataAdapter a = new SqlDataAdapter(cmd))
{
    a.Fill(t1);
}
return t1;
}

and now can be used like this:

table = GetDataTable();

You can fill your data table like the below code.I am also fetching the connections at runtime using a predefined XML file that has all the connection.

  public static DataTable Execute_Query(string connection, string query)
    {
        Logger.Info("Execute Query has been called for connection " + connection);
        connection = "Data Source=" + Connections.run_singlevalue(connection, "server") + ";Initial Catalog=" + Connections.run_singlevalue(connection, "database") + ";User ID=" + Connections.run_singlevalue(connection, "username") + ";Password=" + Connections.run_singlevalue(connection, "password") + ";Connection Timeout=30;";
        DataTable dt = new DataTable();
        try
        {
            using (SqlConnection con = new SqlConnection(connection))
            {
                using (SqlCommand cmd = new SqlCommand(query, con))
                {
                    con.Open();
                    using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                    {
                        da.SelectCommand.CommandTimeout = 1800;
                        da.Fill(dt);
                    }
                    con.Close();
                }
            }
            Logger.Info("Execute Query success");
            return dt;
        }
        catch (Exception ex)
        {
            Console.Write(ex.Message);
            return null;
        }
    }