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我正在尝试将字符串转换为 xml,但是当代码运行时“值不能为空”,如何解决这个问题?在 Windows Phone 8 中运行的项目

public string baslıkbul(baslıkı ba)
    {
        SqlConnection bag = new SqlConnection(ConfigurationManager.ConnectionStrings["baglantı"].ConnectionString.ToString());
        bag.Open();
        SqlCommand yap = new SqlCommand("select Baslık from AN where AD=@ad",bag);
        yap.Parameters.AddWithValue("@ad", ba.AD);
        yap.ExecuteNonQuery();
        SqlDataAdapter da = new SqlDataAdapter(yap);
        DataSet ds = new DataSet();
        da.Fill(ds);
        string s = ds.GetXml(); /// this line is running

        XmlReader okuyucu = XmlReader.Create(new StringReader(s));
        while(okuyucu.Read())
        {
            if(okuyucu.NodeType==XmlNodeType.Element)
            {
                switch(okuyucu.Name)
                {
                    case"Baslık":
                        s = Convert.ToString(okuyucu.ReadString());

                        s = ba.Baslık;
                        break;
                }
            }
        }


        bag.Close();
        return ba.Baslık;
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1 回答 1

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您提供给ad参数(即ba.AD)的值很可能是null. 如果这是您想要在 WHERE 子句中用于过滤的值,那么您应该改为传递System.DBNull

于 2015-07-14T16:48:16.003 回答