连接属性的错误尚未初始化

Question

嗯，我用C＃工作一点点，现在我开始用C＃处理数据库，我在几个地方搜索了一下，我无法确定它在哪里错误的，无处不在说我需要打开连接，但它已经打开。

 SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\v11.0;Integrated Security=True;AttachDbFilename=C:\Users\Gustavo\Documents\Visual Studio 2013\Projects\hour\hour\Database1.mdf"); 
     con.Open(); 
     try 
     { 
      string query = "INSERT INTO [Table] (name, time) VALUES ('test',1)"; 
      SqlCommand cmd = new SqlCommand(query); 
      cmd.ExecuteNonQuery(); 
     } 
     catch (Exception ex) 
     { 
      MessageBox.Show(ex.ToString()); 
     } 

Answer 1

使用using，负责关闭和处置你，以防万一你忘记明确地做到这一点。把它放在try里面，你在try之外有连接open命令，所以它不会捕获任何连接错误。你可能也想看看参数化你的命令。

using (SqlConnection conn = new SqlConnection(@"Data Source=(LocalDB)\v11.0;Integrated Security=True;AttachDbFilename=C:\Users\Gustavo\Documents\Visual Studio 2013\Projects\hour\hour\Database1.mdf")) 
{ 
     conn.Open(); 
     using (SqlCommand cmd = new SqlCommand("INSERT INTO [Table] (name, time) VALUES (@name,@time)", conn)) 
     { 
      cmd.Parameters.AddWithValue("@name", "test"); 
      cmd.Parameters.AddWithValue("@time", 1); 
      cmd.CommandType = CommandType.Text; 
      cmd.ExecuteNonQuery(); 
     } 
} 

Answer 2

您需要将命令分配给连接。例如：

private static void ReadOrderData(string connectionString) 
    { 
     string queryString = 
      "SELECT OrderID, CustomerID FROM dbo.Orders;"; 
     using (SqlConnection connection = new SqlConnection(
        connectionString)) 
     { 

//---- 

      SqlCommand command = new SqlCommand(
       queryString, connection); 


//---- 
      connection.Open(); 
      SqlDataReader reader = command.ExecuteReader(); 
      try 
      { 
       while (reader.Read()) 
       { 
        Console.WriteLine(String.Format("{0}, {1}", 
         reader[0], reader[1])); 
       } 
      } 
      finally 
      { 
       // Always call Close when done reading. 
       reader.Close(); 
      } 
     } 
    } 

Answer 3

SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\v11.0;Integrated Security=True;AttachDbFilename=C:\Users\Gustavo\Documents\Visual Studio 2013\Projects\hour\hour\Database1.mdf"); 
     try 
     { 
      string query = "INSERT INTO [Table] (name, time) VALUES ('test',1)"; 
      SqlCommand cmd = new SqlCommand(query,con); 
      con.Open(); 
      cmd.ExecuteNonQuery(); 
      con.Close(); 
     } 
     catch (Exception ex) 
     { 
      MessageBox.Show(ex.ToString()); 
     }