一个值分配给在DataGridView控制 [英] Assign a value to a control in the datagridview

问题描述

我想这取决于DropDownList的选定值赋值给一个文本框。不过，我试试这个得到的错误

  

对象引用不设置到对象的实例

下面是我的code：

 的foreach（在cgvRequest.Rows GridViewRow GVR）
{
    //编程方式从模板列访问复选框    // CheckBoxField字段CHK =（CheckBoxField字段）gvr.FindControl（chkMark）;
    标签LBL =（标签）gvr.FindControl（lblRequestAmount）;    文本框_txtAmount =（文本框）cgvRequest.FindControl（txtAmount）;    lbl.Text = Convert.ToString（
                   requestinfo.ElementAt（gvr.RowIndex）.AmountRequested）;    DropDownList的DDL =新的DropDownList（）;
    DDL =（DropDownList的）cgvRequest.FindControl（ddlApprovalType）;    ddl.SelectedValue =A;
    _txtAmount.Text = lbl.Text;
}
 

解决方案

这是你所得到的原因

  

对象引用不设置到对象的实例

是控件（DropDownList的和/或文本框）你想设置一个属性来为空。这意味着它无法通过的FindControl找到（）方法。

我只是假设这是因为我不能调试您的code，但我敢打赌，那是因为你正在调用的FindControl 上的数据网格，而不是行

试着改变你的code为：

 文本框_txtAmount =（文本框）gvr.FindControl（txtAmount）;
 

和

  DropDownList的DDL =新的DropDownList（）;
DDL =（DropDownList的）gvr.FindControl（ddlApprovalType）;
 

I want to assign a value to a textbox depending on the selected value of the dropdownlist. But I try this getting the error

"Object reference not set to an instance of an object"

Here is my code:

foreach (GridViewRow gvr in cgvRequest.Rows)
{
    //Programmatically access the CheckBox from the TemplateField

    //CheckBoxField chk = (CheckBoxField)gvr.FindControl("chkMark");
    Label lbl = (Label)gvr.FindControl("lblRequestAmount");

    TextBox _txtAmount = (TextBox)cgvRequest.FindControl("txtAmount");

    lbl.Text = Convert.ToString(
                   requestinfo.ElementAt(gvr.RowIndex).AmountRequested);

    DropDownList ddl = new DropDownList();
    ddl = (DropDownList)cgvRequest.FindControl("ddlApprovalType");

    ddl.SelectedValue = "A";
    _txtAmount.Text = lbl.Text;
}

解决方案

The reason that you are getting

"Object reference not set to an instance of an object"

is that the control (dropdownlist and/or textbox) you are trying to set a property to is null. Which means it cannot be found by FindControl() method.

I am just assuming this because I cannot debug your code, but I bet it is because you are calling FindControl on the data grid and not on the row.

Try changing your code to:

TextBox _txtAmount = (TextBox)gvr.FindControl("txtAmount");

and

DropDownList ddl = new DropDownList();
ddl = (DropDownList)gvr.FindControl("ddlApprovalType");

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