将参数传递到 SqlCommand 时出现问题

Question

我在将参数传递给 SqlCommand 的 SQL 字符串时遇到问题。当我使用选项 1（见下文）时，代码有效。当我使用选项 2 时，它不起作用。我不确定如何让 .AddWithValue 方法与 SqlCommand.

一起使用

如有任何帮助，我们将不胜感激！

private string [] GetOrderInfo (string folder)
{
    string [] order = new string [] { "date", "order#", "storeid", "storename", "username" };

    using (SqlConnection conn = new SqlConnection (_connectionString))
    {
        conn.Open ();

        // Option 1: this line works.
        //string sql = "select * from OrderProduct where OrderProductID=26846";

        // Option 2: this line doesn't work.
        string sql = "select * from OrderProduct where OrderProductID=@folder;";

        using (SqlCommand command = new SqlCommand (sql, conn))
        {
            command.Parameters.AddWithValue ("@folder", folder);

            using (SqlDataReader reader = command.ExecuteReader ())
            {
                while (reader.Read ())
                    order [1] = Convert.ToString (reader.GetInt32 (1));
            }
        }

        conn.Close ();
    } // using (SqlConnection conn = new SqlConnection (connectionString))

    return order;
}

Answer 1

尝试使用

 Command.Parameters.Add("@folder",SqlDbType.Varchar).Value = folder;

Answer 2

您可以试试：

using (SqlCommand command = new SqlCommand("select * from OrderProduct where OrderProductID=@folder", conn))
{
    command.Parameters.Add(new SqlParameter("@folder", folder));

    using (SqlDataReader reader = command.ExecuteReader())
    {
        while (reader.Read())
            order[1] = Convert.ToString(reader.GetInt32(1));
    }
}

Answer 3

AddWithValue 方法使用值的类型来定义正确的 SqlDbType。因此，如果您的字段 OrderProductID 的类型为 INT，您需要添加一个 int.

样本：

command.Parameters.AddWithValue ("@folder", 26846);

另一种简单的方法是使用像 SqlDatabaseCommand or Dapper.

这样的简单对象映射器

using (var cmd = new SqlDatabaseCommand(_connection))
{
    cmd.CommandText.AppendLine(" SELECT * ")
                   .AppendLine("   FROM EMP ")
                   .AppendLine("  WHERE EMPNO = @EmpNo ")
                   .AppendLine("    AND HIREDATE = @HireDate ");

    cmd.Parameters.AddValues(new
            {
                EmpNo = 7369,
                HireDate = new DateTime(1980, 12, 17)
            });

    var emps = cmd.ExecuteTable<Employee>();
}

将参数传递到 SqlCommand 时出现问题

Problems Passing Parameters into SqlCommand

c#

sql

tsql

sql-server

sqlcommand