Gridview中的错误行数据绑定事件 [英] error Row Databound Event in Gridview

问题描述

当我在gridview中进行编辑时，出现此对象引用未设置为对象实例的错误.

这是我的代码.

When i am editing in gridview i am getting error like this Object reference not set to an instance of an object.

Here is my code.

public List<products> GetProducts()
        {
            string query = "Select ProductID, ProductName, UnitPrice, UnitsinStock, CategoryID, Discontinued from Products";
            con = new SqlConnection(cons);
            cmd = new SqlCommand(query, con);
            try
            {
                con.Open();
                dr = cmd.ExecuteReader();
                List<products> lst = new List<products>();
                if (dr.HasRows)
                {
                    while (dr.Read())
                    {
                        Products pd = new Products();
                        pd.Productid = Convert.ToInt32(dr[0]);
                        pd.ProductName = dr[1].ToString();
                        pd.UnitPrice = Convert.ToInt32(dr[2]);
                        pd.UnitsinStock = Convert.ToInt32(dr[3]);
                        pd.CategoryID = Convert.ToInt32(dr[4]);
                        pd.Discontinued = Convert.ToBoolean(dr[5]);
                        lst.Add(pd);
                    }
                }
                return lst;

            }
            catch (Exception ex)
            {
                throw ex;
            }

            finally
            {
                con.Close();
            }
        }

编辑产品-

Edit Product -

protected void EditProduct(object sender, GridViewEditEventArgs e)
       {
           gv.EditIndex = e.NewEditIndex;
           GetProducts();
       }

gv_rowdatabound事件.

gv_rowdatabound event.

protected void gv_RowDataBound(object sender, GridViewRowEventArgs e)
       {
           if (e.Row.RowType == DataControlRowType.DataRow && gv.EditIndex == e.Row.RowIndex)
           {
               DropDownList ddlist = (DropDownList)e.Row.FindControl("ddlcategoryid");
               ddlist.DataSource = cbl.GetCategories();
               ddlist.DataTextField = "CategoryID";
               ddlist.DataValueField = "CategoryName";
               ddlist.DataBind();
               ddlist.Items.FindByValue((e.Row.FindControl("lblcategoryid") as Label).Text).Selected = true;

           }
       }
   }

传递rowdatabound事件后，它会出现 this 错误:对象引用未设置为对象的实例.

请帮我谢谢.

[edit]从下面的注释中添加了错误信息(粗体)-Nelek [/edit]

After passing rowdatabound event it is getting this error: Object reference not set to an instance of an object.

Please help me thank you.

[edit] Added error information from comment below (bold) - Nelek [/edit]

推荐答案

在您的代码中验证以下内容:-
-调用GetCategories完成时，lblcategoryid文本应作为ddlist中的值出现
-标签的第二个检查文本大小写(下部或上部).它应该与dropDown值相同.
您可以在使用"FindByValue()"之前进行检查

verify these things in your code :-
- lblcategoryid text should be present as a value in ddlist while you are calling completed of GetCategories
- second one check text case(lower or upper) of label. it should be same as dropDown Value.
you can check before using "FindByValue()"

string str1 =  ddlist.SelectedValue;  //"product1"
string str2 = e.Row.FindControl("lblcategoryid") as Label).Text // "Product1"

我对我的问题感到满意.我添加了objectdatasource，并保持了dropdownlist selectedvalue
这是我的解决方法.

I soleved my problem. i added objectdatasource and i kept dropdownlist selectedvalue
here is my solution.

<asp:GridView ID="gv" runat="server" AutoGenerateColumns="false"

           DataKeyNames="CustomerID" OnRowEditing="EditCustomer"

           onrowcancelingedit="gv_RowCancelingEdit"

           onrowupdating="gv_RowUpdating">
           <Columns>
              <asp:CommandField ShowEditButton="true" ShowDeleteButton="true" />
               <asp:TemplateField HeaderText="CustomerID" SortExpression="CustomerID">
                   <ItemTemplate>
                       <asp:Label ID="lblCustomerid" runat="server" Text='<%# Eval("CustomerID") %>'></asp:Label>
                   </ItemTemplate>
               </asp:TemplateField>
               <asp:TemplateField HeaderText="CustomerName" SortExpression="CustomerName">
                   <ItemTemplate>
                       <asp:Label ID="lblCustomerName" runat="server" Text='<%# Eval("CustomerName") %>'></asp:Label>
                   </ItemTemplate>
                   <EditItemTemplate>
                       <asp:TextBox ID="txtcustomername" runat="server" Text='<%# Bind("CustomerName") %>'></asp:TextBox>
                   </EditItemTemplate>
               </asp:TemplateField>
               <asp:TemplateField HeaderText="City" SortExpression="City">
                   <ItemTemplate>
                       <asp:Label ID="lblcity" runat="server" Text='<%# Eval("City") %>'></asp:Label>
                   </ItemTemplate>
                   <EditItemTemplate>
                       <asp:DropDownList ID="ddlcity" runat="server" AutoPostBack="True"

                           DataSourceID="ObjectDataSource1" DataTextField="City"

                           DataValueField="City" SelectedValue='<%# Bind("City") %>' ></asp:DropDownList>
                   </EditItemTemplate>
               </asp:TemplateField>
           </Columns>
       </asp:GridView>
       <asp:ObjectDataSource ID="ObjectDataSource1" runat="server"

           SelectMethod="GetAddress" TypeName="BusinessLogicLayer.Customersbll">
       </asp:ObjectDataSource>

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