連接字符串上的錯誤

Question

在（connectionString）上有一個紅色的下划線錯誤，它指示名稱“ ConnectionString”在當前上下文中不存在。 使用using語句之前是否需要聲明sth？

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語句中，您想要獲取connectionString值。 但是沒有任何變量。

更改

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

至

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

---

另外，在using語句中沒有結尾括號。

 using (SqlConnection connection = new SqlConnection(connectionString))

Answer 2

如果您完全確定connectionString，請使用以下代碼：

 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

作為你的代碼

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

您正在建立不是connectionstring的連接實例。 使它成為String connectionString並將它們作為參數傳遞給SqlConnection。