Question

当应用程序运行时，我收到错误或冻结，因为它给了我消息：

Must declare the scalar variable "@Category" " next to dashowadscat.Fill(dsadsshowcat);。

在QueryString [＆＃34; cat＆＃34;]

下还有一个红线

  using (SqlConnection shwadscat = new SqlConnection(cs))
          {                   
            shwadscat.Open();

            SqlDataAdapter dashowadscat = 
              new SqlDataAdapter("SELECT DISTINCT [AdsID],
                                         [Section], 
                                         [Category], 
                                         [Country], 
                                         [State], 
                                         [City], 
                                         [AdsTit], 
                                         SUBSTRING([AdsDesc],1,155) as AdsDesc,
                                         [AdsPrice], 
                                         [Img1] 
                                  FROM [ads] 
                                  WHERE (([Category] = @Category) 
                                  AND ([Country] = @Country))", cs);

            string location = Convert.ToString(Session["location"]);
            string cat = Convert.ToString(QueryString["cat"]);

            DataSet dsadsshowcat = new DataSet();

            dashowadscat.Fill(dsadsshowcat);

            cateshowlistview.DataSource = dsadsshowcat.Tables[0];
            cateshowlistview.DataBind();
          }
        }
        else
        {...}

Answer 1

select语句在where子句中需要2个参数，而你没有提供它们。

Answer 2

请检查您的SQL SELECT DISTINCT [AdsID],[Section], [Category], [Country], [State], [City], [AdsTit], SUBSTRING([AdsDesc],1,155) as AdsDesc, [AdsPrice], [Img1] FROM [ads] WHERE (([Category] = @Category) AND ([Country] = @Country))

我相信您希望传递@Category和@Country作为参数，您可以检查SqlParameter，否则，您可以在以下代码中连接SQL：

修改（使用整个代码展开代码，并将cs更改为shwadscat：

using (SqlConnection shwadscat = new SqlConnection(cs))
{
    shwadscat.Open();

    string location = Convert.ToString(Session["location"]);
    string cat = Convert.ToString(QueryString["cat"]);

    SqlDataAdapter dashowadscat = new SqlDataAdapter("SELECT DISTINCT [AdsID],[Section], [Category], [Country], [State], [City], [AdsTit], SUBSTRING([AdsDesc],1,155) as AdsDesc, [AdsPrice], [Img1] FROM [ads] WHERE (([Category] = '" + cat+ "') AND ([Country] = '" + location + "'))", shwadscat);

    DataSet dsadsshowcat = new DataSet();

    dashowadscat.Fill(dsadsshowcat);

    cateshowlistview.DataSource = dsadsshowcat.Tables[0];
    cateshowlistview.DataBind();
}

Answer 3

您尚未声明标量变量@Category，这是一个示例：

SqlCommand cmd = new SqlCommand("SELECT DISTINCT [AdsID],[Section], [Category], [Country], [State], [City], [AdsTit], SUBSTRING([AdsDesc],1,155) as AdsDesc, [AdsPrice], [Img1] FROM [ads] WHERE (([Category] = @Category) AND ([Country] = @Country))", cs);
cmd.Parameters.Add("@Category", SqlDbType.Int);
cmd.Parameters["@ID"].Value = "";
cmd.Parameters.Add("@Country", SqlDbType.Int);
cmd.Parameters["@ID"].Value = "";

Answer 4

一些问题......

您需要在查询字符串中指定参数的值。
我假设您需要Request.QueryString，而不仅仅是QueryString，这本身并不代表任何内容，这就是您收到语法错误的原因。
您当前正在传递SqlDataAdapter连接字符串，而不是您实例化的SqlConnection。如果您的连接字符串适用于SqlDataAdapter，那么您可以完全删除SqlConnection＆＃34; shwadscat＆＃34;。

试试这个：

var location = Convert.ToString(Session["location"]);
var cat = Convert.ToString(Request.QueryString["cat"]);

var dsadsshowcat = new DataSet();

using (SqlConnection shwadscat = new SqlConnection(cs))
{
    shwadscat.Open();

    using (var dashowadscat = new SqlDataAdapter("SELECT DISTINCT AdsID, Section, Category, Country, State, City, AdsTit, SUBSTRING(AdsDesc,1,155) as AdsDesc, AdsPrice, Img1 FROM ads WHERE Category = @Category AND Country = @Country", shwadscat))
    {
        dashowadscat.SelectCommand.Parameters.AddWithValue("@Category", cat);
        dashowadscat.SelectCommand.Parameters.AddWithValue("@Country", location);

        dashowadscat.Fill(dsadsshowcat);

        cateshowlistview.DataSource = dsadsshowcat.Tables[0];
        cateshowlistview.DataBind();
    }
}

通过方式参数化您的查询的荣誉。这是更安全，更易于维护的方式。

数据集出错

4 个答案: