为什么无法识别我的SqlParameter？

问题描述

我收到此错误：

System.Data.SqlClient.SqlException：'参数化查询'（@inputKarakterSoort varchar（8000））SELECT TOP 2 * FROM Karakter'需要未提供的参数'@inputKarakterSoort'。

但是我想我已经给出了参数化查询。

我的DAL：

public class SortedKarakterContext : ISortedKarakterContext
{
        public string conn { get; set; }

        public SortedKarakterContext()
        {
            this.conn = "MYCONNECTIONSTRING";
        }

        private SqlConnection GetConnection()
        {
            return new SqlConnection(conn);
        }

        public IEnumerable<KarakterDTO> GetSortedKarakters(string inputKarakterSoort)//User input was not supplied?? Hoe veranderen
        {
            using (SqlConnection connection = GetConnection())
            {
                connection.Open();
                var command = new SqlCommand("SELECT TOP 2 * FROM Karakter WHERE KarakterSoort = @inputKarakterSoort ORDER BY NEWID();",connection);
                command.Parameters.Add("@inputKarakterSoort",SqlDbType.VarChar).Value = inputKarakterSoort;
                var reader = command.ExecuteReader();
                var sortedKarakters = new List<KarakterDTO>();

                while (reader.Read())
                {
                    var karakter = new KarakterDTO
                    {
                        KarakterId = (int)reader["KarakterId"],KarakterSoort = reader["KarakterSoort"]?.ToString(),KarakterNaam = reader["KarakterNaam"]?.ToString()
                    };

                    sortedKarakters.Add(karakter);
                }

                return sortedKarakters;
            }
        }
    }
}

我以为我是在这一行完成的：

   command.Parameters.Add("@inputKarakterSoort",SqlDbType.VarChar).Value = inputKarakterSoort;

我确定inputKaraktersoort具有值，因为当我在其中放置断点时，它说它具有正确的值。

错误在此行上：

var reader = command.ExecuteReader();

有人可以帮助我吗？

根据请求，输入命令值和inputKarakterSoort：

当我键入此内容时：

 inputKarakterSoort = "Defensive"

上方：connection.Open()

它确实有效，但是我想在查询中输入参数。

解决方法

我尝试了sgmoore的评论并实施了它。现在可以使用。

这是我的DAL：

public class SortedKarakterContext : ISortedKarakterContext
{
        public string conn { get; set; }

        public SortedKarakterContext()
        {
            this.conn = "MYCONNECTIONSTRING";
        }

        private SqlConnection GetConnection()
        {
            return new SqlConnection(conn);
        }

        public IEnumerable<KarakterDTO> GetSortedKarakters(string inputKarakterSoort)
        {
            using (SqlConnection connection = GetConnection())
            {
                connection.Open();
                var command = new SqlCommand("SELECT TOP 2 * FROM Karakter WHERE KarakterSoort = @inputKarakterSoort ORDER BY NEWID();",connection);
                if (inputKarakterSoort == null)         
                     command.Parameters.Add("@inputKarakterSoort",SqlDbType.VarChar).Value = DBNull.Value;     
                else        
                     command.Parameters.Add("@inputKarakterSoort",SqlDbType.VarChar).Value = inputKarakterSoort;
                var reader = command.ExecuteReader();
                var sortedKarakters = new List<KarakterDTO>();

                while (reader.Read())
                {
                    var karakter = new KarakterDTO
                    {
                        KarakterId = (int)reader["KarakterId"],KarakterSoort = reader["KarakterSoort"]?.ToString(),KarakterNaam = reader["KarakterNaam"]?.ToString()
                    };

                    sortedKarakters.Add(karakter);
                }

                return sortedKarakters;
            }
        }
    }
}

,

代替使用

var command = new SqlCommand（$“ SELECT TOP 2 * FROM Karakter WHERE KarakterSoort = {inputKarakterSoort} ORDER BY NEWID（）;”，connection）;