My code:

// Get Connection String
string conn = WebConfigurationManager.ConnectionStrings["GraduatesConnectionString"].ToString();
// Create connection object
SqlConnection connection = new SqlConnection(conn);
SqlCommand command = connection.CreateCommand();
try
{
    // Open the connection.
    connection.Open();
    // Execute the insert command.
    command.CommandText = ("INSERT INTO PersonalInfo(Id,Name,LastName,ContactNumber, Address,Gender, Date_Of_Birth) VALUES(\'"
                + (this.txtID.Text + ("\',\'"
                + (this.txtName.Text + ("\',\'"
                + (this.txtLastName.Text + ("\',\'"
                + (this.txtContactNumber.Text + ("\',\'"
                + (this.txtAddress.Text + ("\',\'"
                + (this.gender + ("\',\'"
                + (this.txtDateofBirth.Text + ("\',\'"
             )))));
    command.ExecuteNonQuery();
}
finally
{
    // Close the connection.
    connection.Close();
}