转载：https://blog.csdn.net/weixin_34238633/article/details/86058972
用途：在sqlserver数据库没有连接成功的时候，可以先进行连接测试，连接不成功可以进行弹框展示，避免直接的异常信息展示。

新建ConnectionTestInfo类

using System.Data.SqlClient;
using System.Data;

public class ConnectionTestInfo
    {
        private static SqlConnection mySqlConnection;  //mySqlConnection   is   a   SqlConnection   object
        private static string ConnectionString = "";
        private static bool IsCanConnectioned = false;

        /// <summary>
        /// 测试连接数据库是否成功
        /// </summary>
        /// <returns></returns>
        public static bool ConnectionTest()
        {
            //获取数据库连接字符串
            ConnectionString = ConnectionInfo.ConnectionString();
            //创建连接对象
            mySqlConnection = new SqlConnection(ConnectionString);
            //ConnectionTimeout 在.net 1.x 可以设置 在.net 2.0后是只读属性，则需要在连接字符串设置
            //如：server=.;uid=sa;pwd=;database=PMIS;Integrated Security=SSPI; Connection Timeout=30
            //mySqlConnection.ConnectionTimeout = 1;//设置连接超时的时间
            try
            {
                //Open DataBase
                //打开数据库
                mySqlConnection.Open();
                IsCanConnectioned = true;
            }
            catch
            {
                //Can not Open DataBase
                //打开不成功 则连接不成功
                IsCanConnectioned = false;
            }
            finally
            {
                //Close DataBase
                //关闭数据库连接
                mySqlConnection.Close();
            }
            //mySqlConnection   is   a   SqlConnection   object
            if (mySqlConnection.State == ConnectionState.Closed || mySqlConnection.State == ConnectionState.Broken)
            {
                //Connection   is   not   available 
                return IsCanConnectioned;
            }
            else
            {
                //Connection   is   available 
                return IsCanConnectioned;
            }
        }
    }

其中数据库字符串调用了类ConnectionInfo的方法ConnectionString

public class ConnectionInfo
    {
        public ConnectionInfo() { }

        /// <summary>
        /// 从配置文件中读取数据库联接字符串
        /// </summary>
        /// <returns></returns>
        public static string ConnectionString()
        {
            return (ConfigurationSettings.AppSettings["ConnectionString"]);
        }
    }