使用asp.net根據GridView中的行值更改圖像的文本值

Question

我正在嘗試根據其值更改圖像的行數據。 例如，行值是“七”，則必須用鷹的圖像來更改它。

我嘗試了以下代碼，但收到錯誤消息“對象引用未設置為對象的實例”。

 Private Sub GridView1_RowDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs) Handles GridView1.RowDataBound

    If e.Row.RowType = DataControlRowType.DataRow Then
        Dim myVal As String = e.Row.Cells(10).Text
        If myVal = "1" Then
            Dim img As Image = TryCast(e.Row.FindControl("Image1"), Image)
            img.ImageUrl = "~\images\cat.GIF" 
        ElseIf myVal = "7" Then
            Dim img As Image = TryCast(e.Row.FindControl("Image2"), Image)
            img.ImageUrl = "~\images\eagle.GIF" 
        End If
    End If
End Sub

下面是Gridview的aspx代碼：

<asp:GridView ID="GridView1" runat="server" CellPadding="4" ForeColor="#333333" 
    Height="672px" Width="1037px">
    <RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
    <FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
    <PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
    <SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" ForeColor="#333333" />
    <HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
    <EditRowStyle BackColor="#999999" />
    <AlternatingRowStyle BackColor="White" ForeColor="#284775" />
</asp:GridView>

下面是將csv文件綁定到gridview的代碼：

 Dim csvFileName As String = "DATA.csv"

        'Change this to your csv file path
        Dim pathofcsv As String = strFolder
        Dim conString As String = "Driver={Microsoft Text Driver (*.txt; *.csv)};Dbq=" + pathofcsv + ";Extensions=csv"
        ds = New DataSet("MyDataSet")
        Dim adp As New OdbcDataAdapter()
        Using conn As New OdbcConnection(conString)
            Using cmd As New OdbcCommand(Convert.ToString("SELECT * FROM ") & csvFileName, conn)
                conn.Open()
                adp.SelectCommand = cmd
                adp.Fill(ds)
            End Using
        End Using

        grid.DataSource = ds
        grid.DataBind()
        grid.Rows(0).Visible = False


        'Rename Columns Names
        With grid.HeaderRow
            .Cells(0).Text = "ANIMAL NAME"
            .Cells(1).Text = "VALUE NO."
        End With

其中“ VALUE NO。” 是my.resources中圖像存儲的數量。

提前致謝。

Answer 1

看起來這兩行會產生錯誤：

Dim img As Image = TryCast(e.Row.FindControl("Image1"), Image)
Dim img As Image = TryCast(e.Row.FindControl("Image2"), Image)

由於數據來自csv，因此您需要在aspx代碼中添加Image1 ：

<asp:GridView ID="GridView1" runat="server" CellPadding="4" ForeColor="#333333" 
    Height="672px" Width="1037px">
    <RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
    <FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
    <PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
    <SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" ForeColor="#333333" />
    <HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
    <EditRowStyle BackColor="#999999" />
    <AlternatingRowStyle BackColor="White" ForeColor="#284775" />
    <Columns>
        <asp:TemplateField HeaderText="Image">
            <ItemTemplate>
                <asp:Image ID="Image1" runat="server" />
            </ItemTemplate>
        </asp:TemplateField>  
    </Columns>
</asp:GridView>

並刪除此行：

Dim img As Image = TryCast(e.Row.FindControl("Image2"), Image)

將Image1插入到GridView1 ，您需要從第10列而不是第9列獲取myVal ：

Dim myVal As String = e.Row.Cells(11).Text

為了避免重復，您只需要在If塊之前聲明img一次：

Private Sub GridView1_RowDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs) Handles GridView1.RowDataBound
    If e.Row.RowType = DataControlRowType.DataRow Then
        Dim myVal As String = e.Row.Cells(11).Text
        Dim img As Image = TryCast(e.Row.FindControl("Image1"), Image)
        If myVal = "1" Then
            img.ImageUrl = "~\images\cat.GIF" 
        ElseIf myVal = "7" Then
            img.ImageUrl = "~\images\eagle.GIF" 
        End If
    End If
End Sub