在 ASP.NET 中更新数据时出错

Question

当我尝试更新时，我无法弄清楚给定代码的确切问题。

protected void UpdateService(object sender, GridViewUpdateEventArgs e)
    {
        int ServiceId = Convert.ToInt32(((Label)GridView1.Rows[e.RowIndex].FindControl("lblServiceID")).Text);
        string ServiceName = ((TextBox)GridView1.Rows[e.RowIndex].FindControl("txtService")).Text;
        decimal Rate = Convert.ToDecimal(((TextBox)GridView1.Rows[e.RowIndex].FindControl("txtRate")).Text);
        string ParentService = ((DropDownList)GridView1.Rows[e.RowIndex].FindControl("ddlParentService")).SelectedItem.Text;
        string GrandParentService = ((DropDownList)GridView1.Rows[e.RowIndex].FindControl("ddlGrandParentService")).SelectedItem.Text;

        SqlConnection con = new SqlConnection(strConnString);
        SqlCommand cmd = new SqlCommand();
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = "update Service set ServiceName=@ServiceName,Rate=@Rate,"+
        "ParentService=@ParentService,GrandParentService=@GrandParentService "+
        "where ServiceId = @ServiceId;" +
         "select ServiceId,GrandParentService,ParentService,ServiceName,Rate from Service";
        cmd.Parameters.Add("@ServiceName", SqlDbType.VarChar).Value = ServiceName;
        cmd.Parameters.Add("@Rate", SqlDbType.Decimal).Value = Rate;
        cmd.Parameters.Add("@ParentService", SqlDbType.VarChar).Value = ParentService;
        cmd.Parameters.Add("@GrandParentService", SqlDbType.VarChar).Value = GrandParentService;


        GridView1.EditIndex = -1;
        GridView1.DataSource = GetData(cmd);
        GridView1.DataBind();
    }



private DataTable GetData(SqlCommand cmd)
    {
        DataTable dt = new DataTable();
        SqlConnection con = new SqlConnection(strConnString);
        SqlDataAdapter sda = new SqlDataAdapter();
        cmd.CommandType = CommandType.Text;
        cmd.Connection = con;
        con.Open();
        sda.SelectCommand = cmd;
        sda.Fill(dt);                    //Error "Must declare the scalar variable "@ServiceId".
        return dt;
    }

我收到一条错误消息“必须在更新时声明标量变量“@ServiceId”。“ServiceId”是表的主键。

请帮助我。提前致谢。

Answer 1

您在查询中指定了 @ServiceId 参数，但从未在命令中声明或添加参数。您需要在执行更新时指定此项，或在插入新行时省略 where 子句。

cmd.CommandText = "update Service set ServiceName=@ServiceName,Rate=@Rate,"+
    "ParentService=@ParentService,GrandParentService=@GrandParentService "+
    "where ServiceId = @ServiceId;" +
     "select ServiceId,GrandParentService,ParentService,ServiceName,Rate from Service";
cmd.Parameters.Add("@ServiceName", SqlDbType.VarChar).Value = ServiceName;
cmd.Parameters.Add("@Rate", SqlDbType.Decimal).Value = Rate;
cmd.Parameters.Add("@ParentService", SqlDbType.VarChar).Value = ParentService;
cmd.Parameters.Add("@GrandParentService", SqlDbType.VarChar).Value = GrandParentService;
cmd.Parameters.Add("@ServiceId", SqlDbType.Int).Value = 1; //Some Value

Answer 2

您的查询有一个名为 @ServiceId 的参数：

cmd.CommandText = "update Service set ServiceName=@ServiceName,Rate=@Rate,"+
"ParentService=@ParentService,GrandParentService=@GrandParentService "+
"where ServiceId = @ServiceId;" +  // <--- right here
 "select ServiceId,GrandParentService,ParentService,ServiceName,Rate from Service";

但你从不添加这样的参数：

cmd.Parameters.Add("@ServiceName", SqlDbType.VarChar).Value = ServiceName;
cmd.Parameters.Add("@Rate", SqlDbType.Decimal).Value = Rate;
cmd.Parameters.Add("@ParentService", SqlDbType.VarChar).Value = ParentService;
cmd.Parameters.Add("@GrandParentService", SqlDbType.VarChar).Value = GrandParentService;

对于 SQL 代码，@ServiceId 是一个从未声明或赋值的变量，因此会出现错误。您需要为其添加一个参数：

cmd.Parameters.Add("@ServiceId", SqlDbType.Int).Value = ServiceId;

Answer 3

看起来 ServiceId 没有被赋予一个值，即使 @ServiceId 在你的 WHERE 子句中。

您正在为 ServiceName 添加一个参数，而不是为 ServiceId 添加一个参数

Answer 4

添加这个

cmd.Parameters.Add("@ServiceId", SqlDbType.Int).Value = ServiceId ;