Question

从数据库中检索字符串值时出现此错误。我正在转换为字符串值。

此代码在VS 2005和VS 2008中有效，但是当我尝试在VS 2017中运行它时，出现错误。

这是代码

       private void GetExplanation(Card c, int position)
        {
            SqlCommand cmd = new SqlCommand
            {
                CommandText = "usp_PCGetExplanation"
            };
            cmd.Parameters.Add("@positionID", SqlDbType.VarChar);
            cmd.Parameters.Add("@cardNumber", SqlDbType.Int);
            cmd.Parameters["@positionID"].Value = position;
            cmd.Parameters["@cardNumber"].Value = c.CardValue + 1;
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Connection = conn;

            try
            {
                conn.Open();


                SqlDataReader rdr = cmd.ExecuteReader();
                rdr.Read();

                if (rdr.HasRows)
                {
                    c.Explanation = rdr.GetString(0);
                }
                else
                {
                    MessageBox.Show("Unable to get explanation");
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(string.Format(
                    "Error retrieving explanation {0}", ex.Message));
            }
            finally
            {
                conn.Close();
                cmd.Dispose();
            }
        }

这是 Card 类属性

    public class Card
    {
        public static string[] faceValues = {"Ace", "Two", "Three", "Four",
                                            "Five", "Six", "Seven", "Eight",
                                            "Nine", "Ten", "Jack", "Queen", "King"};

        public static string[] suits = { "Hearts", "Clubs", "Diamonds", "Spades" };

        private int cardValue;

        private string faceName;
        private string suitName;
        private string explanation;

        public bool isNegative;

        private Image cardPicture;

        private readonly Random rnd = new Random(52);

        public Card(int value)
        {
            cardValue = value;
            faceName = faceValues[(value) % 13];
            suitName = suits[value / 13];
            explanation = " ";
        }

        public int CardValue
        {
            get { return cardValue; }
            set { cardValue = value; }
        }

        public string FaceName
        {
            get { return faceName; }
            set { faceName = value; }
        }

        public string SuitName
        {
            get { return suitName; }
            set { suitName = value; }
        }

        public string Explanation
        {
            get { return explanation; }
            set { explanation = value; }
        }

        public Image CardPicture
        {
            get { return cardPicture; }
            set { cardPicture = value; }
        }

        public int FaceValue
        {
            get { return cardValue % 13; }
        }

        public override string ToString()
        {
            return string.Format("{0} of {1}", FaceName, suitName);
        }
        public bool IsNegative
        {
            get
            {
                if ( suitName == "spades")
                {
                    return true;
                }
                else
                {
                    return false;
                }
            }

        }
    }
}

这是存储过程

USE [PersonalForecast]
GO
/****** Object:  StoredProcedure [dbo].[usp_PCGetExplanation]    Script Date: 3/21/2019 5:28:16 PM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author:      Tom Magaro
-- Create date: 20101214
-- Description: Gets the PositionCard row
-- =============================================
ALTER PROCEDURE [dbo].[usp_PCGetExplanation] 
    -- Add the parameters for the stored procedure here
    @positionId int, 
    @cardNumber int
AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

    -- Insert statements for procedure here
    SELECT Explanation
    FROM   PositionCard
    WHERE  PositionId = @positionId and
           CardId = @cardNumber
    ORDER BY positionId, CardId
END

任何对此的帮助将不胜感激

汤姆

Answer 1

我认为问题出在您的参数类型上。 @positionID可能是int，因为您的参数在存储过程中是int

cmd.Parameters.Add("@positionID", SqlDbType.Int);
cmd.Parameters.Add("@cardNumber", SqlDbType.Int);

c＃参数类型是存储过程参数类型上的匹配项。

Answer 2

错误出在存储过程中。

@positionId int = 0， @cardValue int = 0

应该是

@positionId int， @cardValue int

无法将系统int转换为C＃中的系统字符串

2 个答案: