为什么无法在c＃

Question

这是dll中的一个现有类，用于验证数据库是否存在

public class CheckDataBaseExists
{
    public void CheckDataBase(string Server, string Database_name)
    {
        SqlConnection con = new SqlConnection(@"Data Source=" + Server + ";Initial Catalog=master;Integrated Security=True");
        con.Open();

        con.InfoMessage += connection_InfoMessage;
        SqlCommand comm = new SqlCommand(@"if DB_ID('" + Database_name + "') is null print '" + Database_name + " is not exist !\r\nCreate new database ?'", con);

        SqlDataAdapter adp = new SqlDataAdapter(comm);
        DataTable set = new DataTable();
        adp.Fill(set);

        con.Close();
    }

    public static void connection_InfoMessage( object sender, SqlInfoMessageEventArgs e)
    {
       if( MessageBox.Show(e.Message, e.Source, MessageBoxButtons.YesNoCancel, MessageBoxIcon.Warning) == DialogResult.Yes)
       {
           try
           {

如果数据库不存在，则输入服务器和数据库名称的形式

              #region create form 

           Label creating = new Label();
           creating = new System.Windows.Forms.Label();
           creating.SuspendLayout();
           // 
           // creating
           // 
           creating.AutoSize = true;
           creating.FlatStyle = System.Windows.Forms.FlatStyle.Flat;
           creating.Font = new System.Drawing.Font("Tahoma", 12F);
           creating.Location = new System.Drawing.Point(25, 3);
           creating.Name = "creating";
           creating.Size = new System.Drawing.Size(150, 19);
           creating.TabIndex = 0;
           creating.Text = "Creating database...";


           Form  create_db = new Form();
           create_db.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
           create_db.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
           create_db.BackColor = System.Drawing.Color.White;
           create_db.ClientSize = new System.Drawing.Size(200, 25);
           create_db.ControlBox = false;
           create_db.TopMost = true;
           create_db.Controls.Add(creating);
           create_db.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
           create_db.MaximizeBox = false;
           create_db.MinimizeBox = false;
           create_db.Name = "Create";
           create_db.ShowIcon = false;
           create_db.ShowInTaskbar = false;
           create_db.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
           create_db.Text = "Creating Databse...";
           create_db.ResumeLayout(false);
           create_db.PerformLayout();




           create_db.Controls.Add(creating);

           create_db.ShowDialog();
               #endregion

读取包含数据库名称和服务器的文件

           string[] read_file = File.ReadAllLines(AppDomain.CurrentDomain.BaseDirectory + @"\" + "ConReq.HP");
               string db_src = read_file[2],
                      db_nm = read_file[0].Substring(7, read_file[0].Length - 7),
                      db_server = read_file[1].Substring(7, read_file[1].Length - 7),
                      location = read_file[3];

SQL文件包含使用要创建的数据库名称创建数据库的命令

             string read_DBsql = File.ReadAllText(AppDomain.CurrentDomain.BaseDirectory + @"\Required\DB\DB.sql");
             read_DBsql = read_DBsql.Replace("DataBaseName", db_nm);

创建连接并执行命令

               SqlConnection con = new SqlConnection("Data Source=" + db_server + ";Initial Catalog=master;Integrated Security=True;MultipleActiveResultSets=True");
               con.Open();
             SqlCommand  comm = con.CreateCommand();
               comm.CommandType = CommandType.Text;
               comm.CommandText = read_DBsql;

               comm.ExecuteNonQuery();
               con.Close();



           }
           catch (Exception db_e)
           {
               MessageBox.Show(db_e.Message, db_e.Source, MessageBoxButtons.OK, MessageBoxIcon.Error);
           }
           }


       }                 
    }

但是发生的是，当出现一条消息时，请确保没有数据库，问题是您是否要创建一个数据库。  当我想创建一个新表单时，出现创建的表单，则什么也没有发生，并且仍然可见。如图所示

Answer 1

为什么要使用Info_Message事件进行最简单的操作（检查数据库）

只需检查结果是否在查询以下：

字符串查询=“从sys.databases中选择count（*），其中name ='dbname'”

执行上述查询：

var count = cmd.ExecuteScalar（）;

还可以请您显示用Info_Message编写的完整代码