网格视图中绑定下拉列表中的错误 [英] error in binding dropdown in grid view

问题描述

我有网格，客户端下拉列表就在那里。编辑网格行时收到错误



请找到以下代码

C＃grid

< asp：TemplateField HeaderText =  客户< span style ='颜色：红色'> * < / span> HeaderStyle-Font-Bold =   true >  
< ItemTemplate> 
< asp：标签ID =   lblClient runat =   server Width =   90 Text = ' <％＃Bind（Client_Name）％>' 
启用=   true CssClass =   control-label >  
 < /   asp：标签 >  
 < span class =code-keyword>< /   ItemTemplate  >  
 < EditItemTemplate中> 
< asp：DropDownList ID =    ddlClients  runat =   server >  < /   asp：DropDownList  >  
< asp：RequiredFieldValidator ID =   frClient runat =   server ErrorMessage =  客户端字段必需 
 ControlToValidate =   ddlClients显示=  无 Text =   * ValidationGroup =   update >  < /   asp：RequiredFieldValidator  >  
 
 
 < /   EditItemTemplate  >  
< HeaderStyle Font-Bold =  < span class =code-string> True >  < /   HeaderStyle  >  
 
 < /   asp：TemplateField  >  
 

代码背后

 受保护  void  GrdViewProject_RowDataBound （ object  sender，GridViewRowEventArgs e）
 {
  try  
 { 
 DataRowView drview = e.Row.DataItem  as  DataRowView; 
 
   #region Active Inactive Code 
   if  （e.Row.RowType == DataControlRowType.DataRow）
 {
 CheckBox chk =（CheckBox）e.Row.FindControl（  chkActive）; 
  if （Convert.ToBoolean（drview [  Is_Active]）==  true ）
 {
 chk.Checked = 真; 
} 
  else  
 {
 chk.Checked =  false ; 
} 
} 
   #endregion 
   if （e.Row.RowType == DataControlRowType.DataRow）
 {
 clsProject objProject1 =  new  clsProject（）; 
 DataSet objDataSet1 =  new  DataSet（）; 
 objDataSet1 = objProject1.FetchClients（）; 
 DropDownList ddlClients =（DropDownList）e.Row.FindControl（  ddlClients）; 
  if （objDataSet1.Tables [ 0 ]。Rows.Count >   0 ）
 {
 ddlClients.Items.Clear（）; 
 ddlClients.DataSource = objDataSet1; 
 ddlClients.DataValueField =   Client_ID; 
 ddlClients.DataTextField =   Client_Name; 
 ddlClients.DataBind（）; 
} 
} 
 
} 
  catch （例外情况）
 {
  throw  ex; 
} 
} 
 

错误消息


来自ddlClients.Items.Clear（）的
; line im得到以下错误消息

对象引用未设置为对象的实例

System.NullReferenceException：对象引用未设置为对象的实例。



请给我解决方案

解决方案

如果你需要在编辑模板中找到控件，请检查 DataControlRowState 如下所示

  if （e.Row.RowType == DataControlRowType.DataRow）
 {
  if （（e.Row.RowState& DataControlRowState.Edit）>   0 ）
 {
  //  在此处查找编辑控件...  
  //   DropDownList ddlClients =（DropDownList）e.Row.FindControl（ddlClients）;  
} 
} 

I have grid in that client dropdown is there. while edit the grid row i m getting error

please find below code
C# grid

<asp:TemplateField HeaderText="Client  <span style='color:Red'>*</span>" HeaderStyle-Font-Bold="true">
                           <ItemTemplate>
                               <asp:Label ID="lblClient" runat="server" Width="90" Text='<%#Bind("Client_Name") %>'
                                   Enabled="true" CssClass="control-label">
                               </asp:Label>
                           </ItemTemplate>
                           <EditItemTemplate>
                                 <asp:DropDownList ID = "ddlClients" runat = "server"> </asp:DropDownList>
                               <asp:RequiredFieldValidator ID="frClient" runat="server" ErrorMessage="client field Required"
                                   ControlToValidate="ddlClients" Display="None" Text="*" ValidationGroup="update"></asp:RequiredFieldValidator>


                           </EditItemTemplate>
                           <HeaderStyle Font-Bold="True"></HeaderStyle>

                       </asp:TemplateField>

code behind

protected void GrdViewProject_RowDataBound(object sender, GridViewRowEventArgs e)
   {
       try
       {
           DataRowView drview = e.Row.DataItem as DataRowView;

           #region Active Inactive Code
           if (e.Row.RowType == DataControlRowType.DataRow)
           {
               CheckBox chk = (CheckBox)e.Row.FindControl("chkActive");
               if (Convert.ToBoolean(drview["Is_Active"]) == true)
               {
                   chk.Checked = true;
               }
               else
               {
                   chk.Checked = false;
               }
           }
           #endregion
           if (e.Row.RowType == DataControlRowType.DataRow)
           {
               clsProject objProject1 = new clsProject();
               DataSet objDataSet1 = new DataSet();
               objDataSet1 = objProject1.FetchClients();
               DropDownList ddlClients = (DropDownList)e.Row.FindControl("ddlClients");
               if (objDataSet1.Tables[0].Rows.Count > 0)
               {
                   ddlClients.Items.Clear();
                   ddlClients.DataSource = objDataSet1;
                   ddlClients.DataValueField = "Client_ID";
                   ddlClients.DataTextField = "Client_Name";
                   ddlClients.DataBind();
               }
           }

       }
       catch (Exception ex)
       {
           throw ex;
       }
   }

error message

from ddlClients.Items.Clear(); line i m getting below error message
Object reference not set to an instance of an object
System.NullReferenceException: Object reference not set to an instance of an object.

please give me the solution

解决方案

if you need to find control inside edit template , check for DataControlRowState as below

if (e.Row.RowType == DataControlRowType.DataRow)
  {
    if ((e.Row.RowState & DataControlRowState.Edit) > 0)
    {
        // find edit controls here ...
        //DropDownList ddlClients = (DropDownList)e.Row.FindControl("ddlClients");
    }
}

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