Question

在（connectionString）上有一个错误的红色下划线，表示当前上下文中不存在名称'ConnectionString'。在使用using语句之前，我是否需要声明？

SqlConnection conn = new SqlConnection("Data Source=baaa;Initial Catalog=InventorySystem;Integrated Security=True") ; 

    using (SqlConnection connection = new SqlConnection(connectionString)
    {
        connection.Open();

        using (SqlCommand command = new SqlCommand(
        "SELECT product.P_ID, Product.P_Name,Product.Leadtime, Product.SafetyStockamount," +
        "Monthlysales.Month, Monthlysales.totalsalesamount, (totalsalesamount/30) as Averagedailysales, ((totalsalesamount/30) * Leadtime + SafetyStockamount) as reorderpoint " +
        "FROM Product, Monthlysales " +
        "where Product.P_ID = Monthlysales.P_ID AND Product.P_ID =@P_ID AND Monthlysales.Month =@Month ", connection))
        {

            command.Parameters.Add(new SqlParameter("P_ID", pid));
            command.Parameters.Add(new SqlParameter("Month", Startmonth));
            SqlDataAdapter adapter = new SqlDataAdapter(command);
            DataSet ds = new DataSet();
            adapter.Fill(ds);
            // now you have the data in Dataset ds
        }

Answer 1

在using语句中，您希望获得connectionString的值。但是没有任何变数。

更改

SqlConnection conn = new SqlConnection("Data Source=baaa;Initial Catalog=InventorySystem;Integrated Security=True") ;

到

string connectionString= "Data Source=baaa;Initial Catalog=InventorySystem;Integrated Security=True";

此外，您还没有在using声明中结束括号。

 using (SqlConnection connection = new SqlConnection(connectionString))

Answer 2

如果您完全确定您的connectionString，请使用以下代码：

 using (SqlConnection connection = new SqlConnection("Data Source=baaa;Initial Catalog=InventorySystem;Integrated Security=True"))
    {
        connection.Open();

        using (SqlCommand command = new SqlCommand(
        "SELECT product.P_ID, Product.P_Name,Product.Leadtime, Product.SafetyStockamount," +
        "Monthlysales.Month, Monthlysales.totalsalesamount, (totalsalesamount/30) as Averagedailysales, ((totalsalesamount/30) * Leadtime + SafetyStockamount) as reorderpoint " +
        "FROM Product, Monthlysales " +
        "where Product.P_ID = Monthlysales.P_ID AND Product.P_ID =@P_ID AND Monthlysales.Month =@Month ", connection))
        {

            command.Parameters.Add(new SqlParameter("P_ID", pid));
            command.Parameters.Add(new SqlParameter("Month", Startmonth));
            SqlDataAdapter adapter = new SqlDataAdapter(command);
            DataSet ds = new DataSet();
            adapter.Fill(ds);
        }
    }

Answer 3

作为您的代码

SqlConnection conn = new SqlConnection("Data Source=baaa;Initial Catalog=InventorySystem;Integrated Security=True") ;

您正在创建不是连接字符串的连接实例。使它成为String connectionString并将它们作为参数传递给SqlConnection。

连接字符串错误

3 个答案: