SQL Server连接

</pre><pre name="code" class="html">//需要创建连接对象及Command对象
private static SqlConnection sqlconn;
private static SqlCommand sqlCmd = new SqlCommand();
/// <summary>
/// 打开连接对象
/// </summary>
public static SqlConnection sqlConnection
{
get
{
if (sqlconn == null)
{
sqlconn = new SqlConnection(connectionString);
sqlconn.Open();
}
//state描述连接的状态
else if (sqlconn.State == ConnectionState.Closed)
{
sqlconn.Open();
}
else if (sqlconn.State == ConnectionState.Broken)
{
sqlconn.Close();
sqlconn.Open();
}
return sqlconn;
}
}

/// <summary>
/// 执行指定的sql语句，不需要返回值
/// </summary>
/// <param name="sqlStr"></param>
public static void cmdExecuteNonQuery(string sqlStr)
{

//创建sqlCommand对象 
sqlCmd.Connection = sqlConnection;
sqlCmd.CommandText = sqlStr;
sqlCmd.CommandType = CommandType.Text;

//执行命令
sqlCmd.ExecuteNonQuery();
}

/// <summary>
/// 执行指定的sql语句。返回单值
/// </summary>
/// <param name="sqlStr"></param>
/// <returns></returns>
public static int cmdExecuteScalar(string sqlStr)
{
sqlCmd.Connection = sqlConnection;
sqlCmd.CommandText = sqlStr;
sqlCmd.CommandType = CommandType.Text;
int count = Convert.ToInt32(sqlCmd.ExecuteScalar());
return count;
}


public static SqlDataReader cmdExecuteReader(string sqlstr)
{
sqlCmd.Connection = sqlConnection;
sqlCmd.CommandText = sqlstr;
sqlCmd.CommandType = CommandType.Text;
SqlDataReader dr = sqlCmd.ExecuteReader();

return dr;
}