並未將物件參考設定為物件的執行個體

Question

 public void PSBM()
    {

        string GetBC = DBHelper.ExecuteQuery("select SortCode from Sort where indexid=" + Convert.ToInt32(DropDownList1.SelectedValue));
        string GetMC = DBHelper.ExecuteQuery("select SortCode from Sort where indexid=" + Convert.ToInt32(DropDownList2.SelectedValue));
        string GetSC = DBHelper.ExecuteQuery("select SortCode from Sort where indexid=" + Convert.ToInt32(DropDownList3.SelectedValue));

        if ((GetBC != "") && (GetMC != ""))
        {
            string sqlPSBM = "select * from PSBM where BClass='" + GetBC + "' and MClass='" + GetMC + "' and SClass='" + GetSC + "'";
            DataTable dt = SQLOperate.GetTable(sqlPSBM);

            Equ_name.DataTextField = "ProductName";
            Equ_name.DataValueField = "Prod_NameCode";
            Equ_name.DataSource = dt.DefaultView;
            Equ_name.DataBind();
            DBHelper.SetDDLControlTipMsg(Equ_name);

            string sqlStandard = "select * from PSBM where BClass='" + GetBC + "' and MClass='" + GetMC + "' and SClass='" + GetSC + "' and Prod_NameCode='" + Equ_name.SelectedItem.Value + "'";
            DataTable sS = SQLOperate.GetTable(sqlStandard);

            Type_Size.DataTextField = "Standard";
            Type_Size.DataValueField = "StandardCode";
            Type_Size.DataSource = sS.DefaultView;
            Type_Size.DataBind();
            DBHelper.SetDDLControlTipMsg(Type_Size);

            string sqlBrand = "select * from PSBM where BClass='" + GetBC + "' and MClass='" + GetMC + "' and SClass='" + GetSC + "' and Prod_NameCode='" + Equ_name.SelectedItem.Value + "' and StandardCode='" + Type_Size.SelectedItem.Value + "'";
            DataTable sB = SQLOperate.GetTable(sqlBrand);

            Brand.DataTextField = "Brand";
            Brand.DataValueField = "BrandCode";
            Brand.DataSource = sB.DefaultView;
            Brand.DataBind();
            DBHelper.SetDDLControlTipMsg(Brand);

            string sqlMadeArea = "select * from PSBM where BClass='" + GetBC + "' and MClass='" + GetMC + "' and SClass='" + GetSC + "' and Prod_NameCode='" + Equ_name.SelectedItem.Value + "' and StandardCode='" + Type_Size.SelectedItem.Value + "' and BrandCode='" + Brand.SelectedItem.Value + "'";
            DataTable sM = SQLOperate.GetTable(sqlMadeArea);

            MadeArea.DataTextField = "MadeArea";
            MadeArea.DataValueField = "MadeAreaCode";
            MadeArea.DataSource = sM.DefaultView;
            MadeArea.DataBind();
            DBHelper.SetDDLControlTipMsg(MadeArea);
        }
               

    }
执行到这一句就抱错了，始终找不到原因。("string sqlStandard = "select * from PSBM where BClass='" + GetBC + "' and MClass='" + GetMC + "' and SClass='" + GetSC + "' and Prod_NameCode='" + Equ_name.SelectedItem.Value + "'";
")，大伙帮忙看下。

Answer 1

可以通过断点来检查一下哪个值为Null~  :) 。。我猜测也许是Equ_name.SelectedItem

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Answer 2

dear

只能设定断点检查有哪个变量是null，也很有可能是SQL语句错误，导致有SQL 变量为null

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Answer 3

Hi Tommy,

如果我没有想错的话这个错误就是"未将对象引用设置到对象的实例"这个错误.
在你代码的出错行里面也只有Equ_name.SelectedItem可能出这个错.
在这一行之后设一个断点然后看看Equ_name.SelectedItem是不是值为null. 如果是,再检查你的Equ_name控件相关的代码是否有问题.

祝你快乐每一天,

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Leo Liu [MSFT]
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