C# SQL查询代码

class SqlDbHelper
{
private static SqlConnection conn;
private static string mConnectionString;
private SqlDbHelper(){}

/// <summary>
/// 判断数据库服务器是否存在
/// </summary>
/// <returns> true:存在</br> false:不存在</returns>
public static bool open(string connectionString)
{
mConnectionString = connectionString;
conn = new SqlConnection(connectionString);

try
{
conn.Open();
}
catch (Exception)
{
return false;
}

return true;

}

public static bool isAlive()
{
bool ret = false;

try
{
close();
ret = open(mConnectionString);
}
catch (Exception)
{
ret = false;
}
return ret;
}

/// <summary>
/// 关闭
/// </summary>
public static void close()
{
if (conn != null)
{
if (conn.State == ConnectionState.Open)
{
conn.Close();
conn.Dispose();
}
conn = null;
}
}

/// <summary>
/// 根据参数查询数据库表内容
/// </summary>
/// <param name="cmdText">SQL 语句</param>
/// <param name="values">查询参数</param>
/// <returns>查询表结果DataTable</returns>
public static DataTable executeNonQuery(string cmdText, SqlParameter[] values)
{
try
{
using (SqlCommand cmd = conn.CreateCommand())
{
cmd.CommandText = cmdText;
if (values == null)
{
cmd.Parameters.AddRange(new SqlParameter[] { });
}
else
{
cmd.Parameters.AddRange(values);
}

SqlDataAdapter sd = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
sd.Fill(dt);

return dt;
}
}
catch (Exception)
{
return null;
}
}

}