sqlhelper.cs

aspnet请认真阅读您的文件包然后写出其具体功能(至少要20个字)。

using System;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

/// <summary>
/// The SqlHelper class is intended to encapsulate high performance, 
/// scalable best practices for common uses of SqlClient.
/// </summary>
public sealed class SqlHelper
{
	private SqlHelper(){}

    //Database connection strings
    public static readonly string CONN_STRING = ConfigurationManager.ConnectionStrings["Sql2005Express"].ConnectionString;

    /// <summary>
    /// Execute a SqlCommand that returns a resultset against the database specified in the connection string 
    /// using the provided parameters.
    /// </summary>
    /// <remarks>
    /// e.g.:  
    ///  SqlDataReader r = ExecuteReader(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
    /// </remarks>
    /// <param name="cmdType">the CommandType (stored procedure, text, etc.)</param>
    /// <param name="cmdText">the stored procedure name or T-SQL command</param>
    /// <param name="cmdParms">an array of SqlParamters used to execute the command</param>
    /// <returns>A SqlDataReader containing the results</returns>
    public static SqlDataReader ExecuteReader(CommandType cmdType, string cmdText, params SqlParameter[] cmdParms)
    {
        SqlCommand cmd = new SqlCommand();
        SqlConnection conn = new SqlConnection(CONN_STRING);

        // we use a try/catch here because if the method throws an exception we want to 
        // close the connection throw code, because no datareader will exist, hence the 
        // commandBehaviour.CloseConnection will not work
        try
        {
            PrepareCommand(cmd, conn, null, cmdType, cmdText, cmdParms);
            SqlDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
            cmd.Parameters.Clear();
            return rdr;
        }
        catch
        {
            conn.Close();
            throw;
        }
    }

    /// <summary>
    /// Execute a SqlCommand that returns the first column of the first record against the database specified in the connection string 
    /// using the provided parameters.
    /// </summary>
    /// <remarks>
    /// e.g.:  
    ///  Object obj = ExecuteScalar(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
    /// </remarks>
    /// <param name="cmdType">the CommandType (stored procedure, text, etc.)</param>
    /// <param name="cmdText">the stored procedure name or T-SQL command</param>
    /// <param name="cmdParms">an array of SqlParamters used to execute the command</param>
    /// <returns>An object that should be converted to the expected type using Convert.To{Type}</returns>
    public static object ExecuteScalar(CommandType cmdType, string cmdText, params SqlParameter[] cmdParms)
    {
        SqlCommand cmd = new SqlCommand();

        using (SqlConnection conn = new SqlConnection(CONN_STRING))
        {
            PrepareCommand(cmd, conn, null, cmdType, cmdText, cmdParms);
            object val = cmd.ExecuteScalar();
            cmd.Parameters.Clear();
            return val;
        }
    }

    /// <summary>
    /// Execute a SqlCommand that returns the first column of the first record against an existing database connection 
    /// using the provided parameters.
    /// </summary>
    /// <remarks>
    /// e.g.:  
    ///  Object obj = ExecuteScalar(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
    /// </remarks>
    /// <param name="conn">an existing database connection</param>
    /// <param name="cmdType">the CommandType (stored procedure, text, etc.)</param>
    /// <param name="cmdText">the stored procedure name or T-SQL command</param>
    /// <param name="cmdParms">an array of SqlParamters used to execute the command</param>
    /// <returns>An object that should be converted to the expected type using Convert.To{Type}</returns>
    public static object ExecuteScalar(SqlConnection conn, CommandType cmdType, string cmdText, params SqlParameter[] cmdParms)
    {

        SqlCommand cmd = new SqlCommand();

        PrepareCommand(cmd, conn, null, cmdType, cmdText, cmdParms);
        object val = cmd.ExecuteScalar();
        cmd.Parameters.Clear();
        return val;
    }


    /// <summary>
    /// Prepare a command for execution
    /// </summary>
    /// <param name="cmd">SqlCommand object</param>
    /// <param name="conn">SqlConnection object</param>
    /// <param name="trans">SqlTransaction object</param>
    /// <param name="cmdType">Cmd type e.g. stored procedure or text</param>
    /// <param name="cmdText">Command text, e.g. Select * from Products</param>
    /// <param name="cmdParms">SqlParameters to use in the command</param>
    private static void PrepareCommand(SqlCommand cmd, SqlConnection conn, SqlTransaction trans, CommandType cmdType, string cmdText, SqlParameter[] cmdParms)
    {

        if (conn.State != ConnectionState.Open)
            conn.Open();

        cmd.Connection = conn;
        cmd.CommandText = cmdText;

        if (trans != null)
            cmd.Transaction = trans;

        cmd.CommandType = cmdType;

        if (cmdParms != null)
        {
            foreach (SqlParameter parm in cmdParms)
                cmd.Parameters.Add(parm);
        }
    }
}