[Solved] ASP.Net Error: the type name SqlCommand could not be found in the namespace System.Data.SqlClient

Small Error on coding please correct it

Error1: Form1 does not contain a definition for bindgrid and no accessible extension method in bindgrid accepting a first argument of type form1 would be basic found are you missing a using directive or an assemble reference

Error 2: The type name SqlCommand could not be found in the namespace ystem.data,sqlclient this type has been forwarded to assembly system.data.sqlclient version = 0.0.0.0 cultural=neutral

using System.Linq; 
using System.Text; 
using System.Threading.Tasks; 
using System.Windows.Forms; 
using System.Data; 
using System.Configuration; 
using System.Data.SqlClient;

private void button6_Click(object sender, EventArgs e)
{
    string id = textBox6.Text;
    string name = textBox7.Text;
    string salary = textBox8.Text;
    textBox6.Text = "";
    textBox7.Text = "";
    textBox8.Text = "";
    string query = "INSERT INTO employee VALUES(@employee_id, @employee_name, @employee_salary)";
    string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        using SqlCommand cmd = new SqlCommand(query);
        cmd.Parameters.AddWithValue("@employee_id", id);
        cmd.Parameters.AddWithValue("@employee_name", name);
        cmd.Parameters.AddWithValue("@employee_salary", salary);
        cmd.Connection = con;
        con.Open();
        cmd.ExecuteNonQuery();
        con.Close();
    }
this.BindGrid();