Select specific value from any row,column or cell in a gridview

Question

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I have a gridview of which there is information displayed from two database tables. I want to select the business name from the "Business name" column and the value from the cell based on the row that the user selects 'viewfile' and assign it to a string variable.

Here is my code(note the gridview is not displayed on the page_load but after a 'search content' button is clicked)

C#

protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
        {
           
            try
            {
                switch (e.CommandName)
                {

                    case "view":
                        
                        String name = GridView1.Rows[4].Cells[4].FindControl("Business_Name").ToString(); 
                        string filename = e.CommandArgument.ToString();
                        string path = Server.MapPath("~/BusinessProfilesContent/" + name + "/" + filename);
                        byte[] bts = System.IO.File.ReadAllBytes(path);
                        Response.Clear();
                        Response.ClearHeaders();
                        Response.ContentType = "image";
                        Response.WriteFile(path);
                        Response.Flush();
                        Response.End();
                        break;
                }
            }
            catch (Exception ex)
            {
                Response.Write(ex.Message);

            }
        }

Here is the webform code:

ASP.NET

 <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" 
                        EmptyDataText = "No files uploaded" Width="766px" onrowcommand="GridView1_RowCommand">
    <Columns>
       <asp:BoundField DataField = "Incident_ID" HeaderText = "Incident ID" />
       <asp:BoundField DataField = "Incident_Type_Name" HeaderText = "Incident Type" />
       <asp:BoundField DataField = "Description" HeaderText = "Description" />
       <asp:BoundField DataField = "Date_Time" HeaderText = "Date and time of Upload" />
       <asp:BoundField DataField = "Business_Name" HeaderText = "Business Name" />
       <asp:BoundField DataField = "Provence" HeaderText = "Provence" />
       <asp:BoundField DataField = "County" HeaderText = "County" />
       <asp:BoundField DataField = "Username" HeaderText = "Username" />
       <asp:ImageField DataImageUrlField="File_Path" ControlStyle-Width="100"
        ControlStyle-Height = "100" HeaderText = "Preview Image"/>
        <asp:TemplateField ItemStyle-HorizontalAlign = "Center">
            <ItemTemplate>
               <asp:LinkButton ID="LinkButton1"  runat="server" CausesValidation="false" CommandName="view" CommandArgument = '<%#Eval("FileName")%>' >ViewFile</asp:LinkButton>
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

Posted 26-Feb-14 4:41am

Member 10609511

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ZurdoDev 26-Feb-14 10:43am

Where are you stuck?

Member 10609511 26-Feb-14 11:57am

I am getting error - object reference not set to an instance of an object. Basically depending on which row the users selects the link button 'view file' from I want to take the value of the cell in that row under column 'Business Name'

2 solutions

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CHill60 · Answer 1 · 2014-02-26T07:15:00

Solution 2

According to your comment (not in your original post) you are getting an exception.

Quote:
object reference not set to an instance of an object

I think it is this line that is firing that exception

String name = GridView1.Rows[4].Cells[4].FindControl("Business_Name").ToString();

Firstly, I don't think you need the .FindControl("Business Name") - you don't have a control called that - it's the title of one of your columns... column index 4 in fact.
Secondly, you are always looking at row index 4 on your datagrid ... what if you haven't got 5 rows in there?
Both of these issues could have produced that error.

Now to solve it ...
That parameter GridViewCommandEventArgs e comes in handy for finding the row that was selected...

int i = Convert.ToInt32(e.CommandArgument);
GridViewRow r = GridView1.Rows[i];

Next you want the cell that corresponds to the "Business Name" column - I already know that this is column index 4 so your code becomes

String name = r.Cells[4].Text;

If you don't want to Hard-Code the column number (and you shouldn't want to) have a look at this post on StackOverflow[^] to get the column based on its name

Posted 26-Feb-14 7:15am

CHill60

Updated 26-Feb-14 7:16am

v2

Comments

Member 10609511 26-Feb-14 13:19pm

When I try that I get this error:

Input string was not in a correct format.

It is coming from the line

int i = Convert.ToInt32(e.CommandArgument);

When I run the debugger...

CHill60 26-Feb-14 13:46pm

Strange. When you run the debugger what are the contents of e.CommandArgument?

Member 10609511 26-Feb-14 13:55pm

The contents are the file name eg.123.jpg however I found a solution to the problem online but it seems to select only the first row(row index remains at 0)

int index;
bool bIsConverted = int.TryParse(e.CommandArgument.ToString(), out index);

CHill60 26-Feb-14 14:10pm

In your Webform code try changing your line for CommandArgument to CommandAgument ="<%#((GridViewRow)Container).RowIndex%>" + ";" + %#Eval("FileName")%> />. This will pass in your filename AND the row index. Access the specific argument e.g. string RowId = e.Values["RowIndex"].ToString(); int i = Convert.ToInt32(RowId);
Apologies ... there may be typing errors in this but I can't check it out at the moment

Member 10609511 26-Feb-14 14:43pm

There Seems to be error in your code somewhere, the line:

string RowId = e.CommandArgument.["RowIndex"].ToString();

Gives the error: Identifier expected

Here is what I have in the asp code for gridview:

<itemtemplate>
<asp:LinkButton ID="LinkButton1" runat="server" CausesValidation="false" CommandName="view" CommandArgument = ''<%#((GridViewRow)Container).RowIndex%>' + ';' + '<%#Eval("FileName")%>''>ViewFile

I found this elsewhere but not sure how to implement
ImageButton b = (ImageButton)sender;
GridViewRow row = (GridViewRow)b.NamingContainer;
if (row != null)
{
//Get the Row Index
int rowIndex = row.RowIndex;
//Get the DataKey value
string key = GridView1.DataKeys[rowIndex].Value.ToString();
//Get the Row value of BoundField
string rowValue = row.Cell[0].Text;

}

Member 10609511 26-Feb-14 15:32pm

I have a solution that I have got working by incorporating this code with mine:

LinkButton l = e.CommandSource as LinkButton;
if(l != null)
{
GridViewRow selectedRow = l.NamingContainer as GridViewRow ;
if(selectedRow != null)
{
int intRowIndex = Convert.ToInt32(selectedRow.RowIndex);
}
}

Member 10609511 · Answer 2 · 2014-02-26T09:33:00

C#

protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
        {
           
           
            try
            {
                switch (e.CommandName)
                {

                    case "view":
                        
                        LinkButton l = e.CommandSource as LinkButton; 
                        
                        GridViewRow selectedRow = l.NamingContainer as GridViewRow ;
                        
                        int intRowIndex = Convert.ToInt32(selectedRow.RowIndex);
               
                        GridViewRow row = GridView1.Rows[intRowIndex];
                        String name = Server.HtmlDecode(row.Cells[4].Text); 
                        string filename = e.CommandArgument.ToString();
                        String ext = String.Empty;
                        string path = Server.MapPath("~/BusinessProfilesContent/" + name + "/" + filename);
                        SqlConnection conn;
                        SqlCommand comm;
                        String connectionString = ConfigurationManager.ConnectionStrings["ApplicationServices"].ConnectionString;
                        conn = new SqlConnection(connectionString);
                        comm = new SqlCommand("SELECT Incident.File_Extension FROM Incident	JOIN User_Acc ON user_acc.User_id=incident.user_id JOIN business ON incident.business_id=business.Business_id JOIN incident_type ON incident_type.incident_type_id = incident.incident_type_id WHERE Business.Business_Name = Business.Business_Name AND Incident.FileName=@FileName", conn);
                         comm.Parameters.Add("@FileName", System.Data.SqlDbType.VarChar).Value = e.CommandArgument;
                        conn.Open();
                        SqlDataReader reader = comm.ExecuteReader();
                        while (reader.Read())
                        {
                          ext = reader["File_Extension"].ToString();                            
                        }
                        byte[] bts = System.IO.File.ReadAllBytes(path);
                        Response.Clear();
                        Response.ClearHeaders();
                        if (ext.Equals(".mov", StringComparison.InvariantCultureIgnoreCase))
                        {
                            Response.ContentType = "video/quicktime";
                        }
                        else if (ext.Equals(".jpg", StringComparison.InvariantCultureIgnoreCase))
                        {
                            Response.ContentType = "image/jpeg";
                        }
                        else if (ext.Equals(".jpeg", StringComparison.InvariantCultureIgnoreCase))
                        {
                            Response.ContentType = "image/jpeg";
                        }
                        else if (ext.Equals(".gif", StringComparison.InvariantCultureIgnoreCase))
                        {
                            Response.ContentType = "image/gif";
                        }
                        else if (ext.Equals(".mp2", StringComparison.InvariantCultureIgnoreCase))
                        {
                            Response.ContentType = "video/mpeg";
                        }
                        else if (ext.Equals(".mpa", StringComparison.InvariantCultureIgnoreCase))
                        {
                            Response.ContentType = "video/mpeg";
                        }
                        else if (ext.Equals(".mpe", StringComparison.InvariantCultureIgnoreCase))
                        {
                            Response.ContentType = "video/mpeg";
                        }
                        else if (ext.Equals(".mpeg", StringComparison.InvariantCultureIgnoreCase))
                        {
                            Response.ContentType = "video/mpeg";
                        }
                        else if (ext.Equals(".mpg", StringComparison.InvariantCultureIgnoreCase))
                        {
                            Response.ContentType = "video/mpeg";
                        }
                        else if (ext.Equals(".mpv2", StringComparison.InvariantCultureIgnoreCase))
                        {
                            Response.ContentType = "video/mpeg";
                        }
                        else if (ext.Equals(".qt", StringComparison.InvariantCultureIgnoreCase))
                        {
                            Response.ContentType = "video/quicktime";
                        }
                        else if (ext.Equals(".avi", StringComparison.InvariantCultureIgnoreCase))
                        {
                            Response.ContentType = "video/x-msvideo";
                        }
                        Response.WriteFile(path);
                        Response.Flush();
                        Response.End();
                        break;
                }
            }
            catch (Exception ex)
            {
                Response.Write(ex.Message);

            }
        }