无法将类型为“System.Web.UI.WebControls.TextBox”的对象强制转换为“System.Web.UI.WebControls.Label”。 [英] Unable to cast object of type 'System.Web.UI.WebControls.TextBox' to type 'System.Web.UI.WebControls.Label'.

问题描述

有没有将boundField加入标签...

我使用此代码将boundFied行放入文本框中，我也希望将其添加到标签中但是我收到了一个错误。

这是我的代码：

< asp：GridView ID =   GridView1 runat =  < span class =code-string> server AutoGenerateColumns =   false DataKeyNames =   CustomerID OnPageIndexChanging =   GridView1_PageIndexChanging OnRowCancelingEdit =   GridView1_RowCancelingEdit OnRowDeleting = < span class =code-string>  GridView1_RowDeleting OnRowEditing =   GridView1_RowEditing OnRowUpdating =   GridView1_RowUpdating  >  
< Columns> 
< asp：BoundField DataField =   CompanyName HeaderText =  公司名称 /> 
< asp：BoundField DataField =  地址 HeaderText =   Sddress /> 
< asp：BoundField DataField =   City HeaderText =  城市 /> 
< asp：BoundField DataField =   PostalCode HeaderText =   PostalCode /> 
< asp：BoundField DataField =   Country HeaderText =  国家 /> 
< asp：CommandField ShowEditButton =   true /> 
< asp：CommandField ShowDeleteButton =   true /> 
 < /  列 >  
 < /   asp：GridView   >  

这是c＃代码：

  protected   void  GridView1_RowUpdating（ object  sender，GridViewUpdateEventArgs e）
 {
  int  Customerid = Convert.ToInt32（GridView1.DataKeys [e.RowIndex]。 Value.ToString（））; 
 GridViewRow row =（GridViewRow）GridView1.Rows [e.RowIndex]; 
标签lblID =（标签）row.FindControl（  lblID）; 
 TextBox textCompanyName =（TextBox）row.Cells [ 0 ]。控件[ 0 ]; 
 TextBox textAddress =（TextBox）row.Cells [ 1 ]。控件[ 0 ]; 
 TextBox textCity =（TextBox）row.Cells [ 2 ]。控件[ 0 ]; 
 TextBox textPostalCode =（TextBox）row.Cells [ 2 ]。控件[ 0 ]; 
  //   string country = row.Cells [4] .Text;  
标签lblCountry =（标签）row.Cells [ 4 ]。控件[ 0 ]; 
 ... 
} 

我在这一行收到错误：

标签lblCountry =（标签）行。细胞[4] .Controls [0]; 
任何帮助

解决方案

错误清楚地告诉你，你不能将类型A的对象转换为类型的对象B.

TextBox和Label是两个不同的控件。您将TextBox类型转换为Label，在这种情况下错误是显而易见的。

如果您想获取文本框的值并将其应用于标签，那么以下代码将有所帮助。 />

 var textBoxObj =（TextBox）row.Cells [4] .Controls [0]; 
标签lblCountry = new Label（）{Text = textBoxObj.Text}; 

因为更新时boundfields被转换为文本框。首先，您必须将其作为文本框投射，之后您可以将其值分配给任何标签。



尝试更换

标签lblCountry =（标签）row.Cells [ 4 ]。控件[ 0 ] ; 

with

 TextBox lblCountry =（TextBox）row.Cells [ 4 ]。控制[ 0 ]; 

然后你可以得到像：

标签myLabel = 新标签（）; 
 myLabel.Text = lblCountry.Text.Trim（）; 

Hi,Is there any to get a boundField into a label...
I am using this code to get a boundFied row into a textbox and I want also to get the same into a Label but I am getting an error.
This is my code:

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" DataKeyNames="CustomerID" OnPageIndexChanging="GridView1_PageIndexChanging" OnRowCancelingEdit="GridView1_RowCancelingEdit" OnRowDeleting="GridView1_RowDeleting" OnRowEditing="GridView1_RowEditing" OnRowUpdating="GridView1_RowUpdating">
                <Columns>
                    <asp:BoundField DataField="CompanyName" HeaderText="Company Name" />
                    <asp:BoundField DataField="Address" HeaderText="Sddress" />
                    <asp:BoundField DataField="City" HeaderText="City" />
                    <asp:BoundField DataField="PostalCode" HeaderText="PostalCode" />
                    <asp:BoundField DataField="Country" HeaderText="Country" />
                    <asp:CommandField ShowEditButton="true" />
                    <asp:CommandField ShowDeleteButton="true" />
                </Columns>
            </asp:GridView>

and this the c# code:

protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
        {
            int Customerid = Convert.ToInt32(GridView1.DataKeys[e.RowIndex].Value.ToString());
            GridViewRow row = (GridViewRow)GridView1.Rows[e.RowIndex];
            Label lblID = (Label)row.FindControl("lblID");
            TextBox textCompanyName = (TextBox)row.Cells[0].Controls[0];
            TextBox textAddress = (TextBox)row.Cells[1].Controls[0];
            TextBox textCity = (TextBox)row.Cells[2].Controls[0];
            TextBox textPostalCode = (TextBox)row.Cells[2].Controls[0];
            //string country = row.Cells[4].Text;
            Label lblCountry = (Label)row.Cells[4].Controls[0];
...
}

I am getting an error ont this line:

Label lblCountry = (Label)row.Cells[4].Controls[0];
Any help

解决方案

The error is clearly telling you that you cannot convert an object of type A to an object of type B.
TextBox and Label are two different controls. You are type casting TextBox as a Label, in which case the error is obvious.
If you want to get the value of textbox and apply it to a label, then the following code would help.

var textBoxObj = (TextBox)row.Cells[4].Controls[0];
Label lblCountry = new Label(){ Text = textBoxObj.Text };

Because on updating boundfields are converted into textboxes. First you will have to cast it as a textbox after that you can assign its value to any label.

Try replacing

Label lblCountry = (Label)row.Cells[4].Controls[0];

with

TextBox lblCountry = (TextBox )row.Cells[4].Controls[0];

Then you can have something like:

Label myLabel = new Label();
myLabel.Text = lblCountry.Text.Trim(); 

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