SqlCode (Saving This — Probably What the Teacher Will Cover)

Reposted from: Yin Likun’s QQ Zone

public class SqlCode
{
    /// <summary>
    /// Create the connection string
    /// </summary>
    /// <returns></returns>
    public static SqlConnection DBCon()
    {
        return new SqlConnection(@"server=JACK-PCSQLEXPRESS;database=test;uid=sa;pwd=jack123");
        //Sql authentication
        //Integrated Security = SSPI/Windows authentication
    }

    /// <summary>
    /// Execute a query
    /// </summary>
    /// <param name="SQLString">Sql query (Select)</param>
    /// <returns></returns>
    public static DataSet Query(string SQLString)
    {
        using (SqlConnection conn = DBCon())
        {
            DataSet ds = new DataSet();
            try
            {
                conn.Open();
                SqlDataAdapter command = new SqlDataAdapter(SQLString, conn);
                command.Fill(ds, "ds");
                command.Dispose();
                conn.Close();
            }
            catch (System.Data.SqlClient.SqlException ex)
            {
                throw new Exception(ex.Message);
            }
            return ds;
        }//when the connection object reaches this point it is disposed, helping memory reclamation
    }

    /// <summary>
    /// Execute insert, delete, update
    /// </summary>
    /// <param name="Sql">including Insert, Delete, Update</param>
    public static void InOrDelOrUp(string Sql)//insert data / delete data / update data
    {
        SqlConnection conn = DBCon();
        conn.Open();
        SqlCommand cmd = new SqlCommand(Sql, conn);
        cmd.ExecuteNonQuery();
        cmd.Dispose();
        conn.Close();
    }

    /// <summary>
    /// Check whether it exists
    /// </summary>
    /// <param name="Username">string</param>
    /// <returns></returns>
    public static bool CheckName(string Username)
    {
        SqlConnection conn = DBCon();
        conn.Open();
        SqlCommand cmd = new SqlCommand("select * from stu where sName='" + Username + "'", conn);
        cmd.ExecuteNonQuery();
        if (null != cmd.ExecuteScalar())
        {
            cmd.Dispose();
            conn.Close();
            return false;
        }
        else
        {
            cmd.Dispose();
            conn.Close();
            return true;
        }
    }
}