错误在ASP.NET中更新数据 [英] Error Updating data in ASP.NET

问题描述

当我尝试更新时，我无法弄清楚给定代码的确切问题。

 受保护  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））。文字; 
  decimal  Rate = Convert.ToDecimal（（（TextBox）GridView1.Rows [e.RowIndex] .FindControl（   txtRate））。文字）; 
  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 + 
  其中ServiceId = @ServiceId; + 
  选择ServiceId，GrandParentService，ParentService，ServiceName，Service from Service; 
 cmd.Parameters.Add（  @ ServiceName，SqlDbType.VarChar）.Value =服务名称; 
 cmd.Parameters.Add（  @ Rate，SqlDbType.Decimal）.Value =率; 
 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（）; 
} 
 
 
 
 私有 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）;  //  错误必须声明标量变量@ServiceId。 
 返回 dt; 
} 

我收到一条错误消息必须在更新时声明标量变量@ServiceId。



请帮帮我。在此先感谢。

解决方案

该异常意味着您没有将命名变量声明为命令的参数。



你需要加上这个：

 cmd.Parameters.Add（@ ServiceId，SqlDbType.VarChar）.Value = 它的价值; 

如果您不会声明该变量并为其赋值，因此您不能将其用作WHERE子句中的参数。您可以选择完全删除它或添加变量。

正如我在您的代码中看到的那样。你在where子句中使用@ServiceId



其中ServiceId = @ ServiceId;

你不是将值传递给此参数

使用以下

 cmd.Parameters。添加（  @ ServiceId，SqlDbType.YourDatatype）.value = yourValue ; 

I am unable to figure out the exact problem of the given code when i try to update.

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;
        }

I am getting an error message "Must declare the scalar variable "@ServiceId" at the time of update.

Please help me. Thanks in advance.

解决方案

That exception means you are not declaring the named variable as a parameter of your command.

You need to add this:

cmd.Parameters.Add("@ServiceId", SqlDbType.VarChar).Value = "the value for it";

[EDIT]

If you are not going to declare that variable and give it a value, then you cannot use it as a parameter in your WHERE clause. Your options are to remove it completely or add the variable.

As i can see in your code. You are using @ServiceId in your where clause

where ServiceId = @ServiceId;
and you are not passing value to this parameter
use below

cmd.Parameters.Add("@ServiceId", SqlDbType.YourDatatype).value=yourValue;

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