C# DataRowView错误对象引用未设置为对象的实例

我正在尝试在我的网站上为我的用户创建一个个人资料页面，在那里他们可以编辑他们的个人资料。我使用了此代码，但它不起作用

    <br />
    <br />

E Mail&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
      <asp:TextBox ID="TextBox4" runat="server" style="width:250px; height:25px; border:thin solid #0099FF"></asp:TextBox>
    <br />
    <br />

    <br />
    <br />

Listings Remaining&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
    <asp:Label ID="Label2" runat="server" Text=""></asp:Label>
    <br />
    <br />
    <br />
    <asp:Button ID="Button1" runat="server" Text="Update" CssClass="button" 
        Width="115px" onclick="Button1_Click" />
    <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:ConnectionString1 %>"
SelectCommand="SELECT fname, cmpny, weblnk, email, cntct, lctn, cdscrptn, bsnstp FROM orgs WHERE (cmpny = @cmpny)"
UpdateCommand="Update [orgs] Set [fname]=@fname,[weblnk]=@weblnk,[email]=@email,[cntct]=@cntct,[lctn]=@lctn,[cdscrptn]=@cdscrptn,[bsnstp]=@bsnstp WHERE [cmpny]=@cmpny">
<SelectParameters>
    <asp:QueryStringParameter Name="cmpny" Type="String" QueryStringField="cmpny" />
</SelectParameters>
<UpdateParameters>
    <asp:Parameter Name="fname" Type="String" />
    <asp:Parameter Name="weblnk" Type="String" />
    <asp:Parameter Name="email" Type="String" />
    <asp:Parameter Name="cntct" Type="String" />
    <asp:Parameter Name="lctn" Type="String" />
    <asp:Parameter Name="cdscrptn" Type="String" />
    <asp:Parameter Name="bsnstp" Type="String" />
    <asp:Parameter Name="cmpny" />
</UpdateParameters>

ASPX页
欢迎 ,

    <br />

Full Name&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    <asp:TextBox ID="TextBox1" runat="server" style="width:250px; height:25px; border:thin solid #0099FF"></asp:TextBox>
    <br />
    <br />
    Company Name&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 

    <asp:TextBox ID="TextBox2" runat="server" style="width:250px; height:25px; border:thin solid #0099FF"></asp:TextBox>
&nbsp;<br />
    <br />

    <br />
    <br />

E Mail&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
      <asp:TextBox ID="TextBox4" runat="server" style="width:250px; height:25px; border:thin solid #0099FF"></asp:TextBox>
    <br />
    <br />

    <br />
    <br />

Listings Remaining&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
    <asp:Label ID="Label2" runat="server" Text=""></asp:Label>
    <br />
    <br />
    <br />
    <asp:Button ID="Button1" runat="server" Text="Update" CssClass="button" 
        Width="115px" onclick="Button1_Click" />
    <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:ConnectionString1 %>"
SelectCommand="SELECT fname, cmpny, weblnk, email, cntct, lctn, cdscrptn, bsnstp FROM orgs WHERE (cmpny = @cmpny)"
UpdateCommand="Update [orgs] Set [fname]=@fname,[weblnk]=@weblnk,[email]=@email,[cntct]=@cntct,[lctn]=@lctn,[cdscrptn]=@cdscrptn,[bsnstp]=@bsnstp WHERE [cmpny]=@cmpny">
<SelectParameters>
    <asp:QueryStringParameter Name="cmpny" Type="String" QueryStringField="cmpny" />
</SelectParameters>
<UpdateParameters>
    <asp:Parameter Name="fname" Type="String" />
    <asp:Parameter Name="weblnk" Type="String" />
    <asp:Parameter Name="email" Type="String" />
    <asp:Parameter Name="cntct" Type="String" />
    <asp:Parameter Name="lctn" Type="String" />
    <asp:Parameter Name="cdscrptn" Type="String" />
    <asp:Parameter Name="bsnstp" Type="String" />
    <asp:Parameter Name="cmpny" />
</UpdateParameters>

---

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

哪一行引发异常？DataRowView row=dv[0]；听起来你好像没有数据。。。。因此为空。欢迎使用堆栈溢出！几乎所有

NullReferenceException

的情况都是相同的。请参阅“”以获取一些提示。我没有数据是什么意思

    <br />
    <br />

E Mail&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
      <asp:TextBox ID="TextBox4" runat="server" style="width:250px; height:25px; border:thin solid #0099FF"></asp:TextBox>
    <br />
    <br />

    <br />
    <br />

Listings Remaining&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
    <asp:Label ID="Label2" runat="server" Text=""></asp:Label>
    <br />
    <br />
    <br />
    <asp:Button ID="Button1" runat="server" Text="Update" CssClass="button" 
        Width="115px" onclick="Button1_Click" />
    <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:ConnectionString1 %>"
SelectCommand="SELECT fname, cmpny, weblnk, email, cntct, lctn, cdscrptn, bsnstp FROM orgs WHERE (cmpny = @cmpny)"
UpdateCommand="Update [orgs] Set [fname]=@fname,[weblnk]=@weblnk,[email]=@email,[cntct]=@cntct,[lctn]=@lctn,[cdscrptn]=@cdscrptn,[bsnstp]=@bsnstp WHERE [cmpny]=@cmpny">
<SelectParameters>
    <asp:QueryStringParameter Name="cmpny" Type="String" QueryStringField="cmpny" />
</SelectParameters>
<UpdateParameters>
    <asp:Parameter Name="fname" Type="String" />
    <asp:Parameter Name="weblnk" Type="String" />
    <asp:Parameter Name="email" Type="String" />
    <asp:Parameter Name="cntct" Type="String" />
    <asp:Parameter Name="lctn" Type="String" />
    <asp:Parameter Name="cdscrptn" Type="String" />
    <asp:Parameter Name="bsnstp" Type="String" />
    <asp:Parameter Name="cmpny" />
</UpdateParameters>