Accessing data from a BoundField of Gridview

I have a GridView like this

<asp:GridView ID="gv_FilesList" runat="server" AutoGenerateColumns="false" onrowcommand="gv_FilesList_RowCommand">
  <Columns>
    <asp:BoundField DataField="f_Id" Visible="false" HeaderText="File Name" />
  </Columns>  
  <Columns>
   <asp:BoundField DataField="f_Nam开发者_C百科e" HeaderText="File Name" />
  </Columns>                                      
  <Columns>
    <asp:ButtonField ButtonType="Link" Text="Download" CommandName="DownloadFile" HeaderText="Download" />
  </Columns>
</asp:GridView>

Now when I click on the download Button, how can I get the corresponding f_Id in order to get the related data from Database.

This code should work, tested on my local.

First, add DataKeyNames to your GridView.

<asp:GridView ID="gv_FilesList" runat="server" AutoGenerateColumns="false" onrowcommand="gv_FilesList_RowCommand" DataKeyNames="f_Id">
  <Columns>
    <asp:BoundField DataField="f_Id" Visible="false" HeaderText="File Name" />
  </Columns>  
  <Columns>
   <asp:BoundField DataField="f_Name" HeaderText="File Name" />
  </Columns>                                      
  <Columns>
    <asp:ButtonField ButtonType="Link" Text="Download" CommandName="DownloadFile" HeaderText="Download" />
  </Columns>
</asp:GridView>

Then, access DataKeys from codebehind.

protected void gv_FilesList_RowCommand(object sender, GridViewCommandEventArgs e)
{
    if (e.CommandName == "DownloadFile")
    {
        //row index
        int index = Convert.ToInt32(e.CommandArgument);

        //retrieve f_Id    
        int f_Id = Convert.ToInt32(gv_FilesList.DataKeys[index].Value);

        //download file with f_Id
        DownloadFile(f_Id);
    }
}

A couple of ways to skin it, but you could access it like below:

void gv_FilesList_RowCommand(Object sender, GridViewCommandEventArgs e) {
   if(e.CommandName=="DownloadFile")
     int index = Convert.ToInt32(e.CommandArgument);
     GridViewRow row = gv_FilesList.Rows[index];
     string fileDownloadId = row.Cells[1].Text;
     //Pull from DB
}

And then add f_id, to the DataKeyNames attribute so it will store the hidden fields value.

<asp:GridView ID="gv_FilesList" runat="server" AutoGenerateColumns="false" onrowcommand="gv_FilesList_RowCommand" DataKeyNames="f_id">

DataKeyNames

A solution to your problem is described in this thread. Basically you can access the row index in the event argument property called CommandArgument.