How to change a value of a control in EditItemTemplate in GridView

Question

Hi I have a GridView control and in it a TextBox control inside an EditItemTemplate Field.
Now I need to change the textbox text when the user enters the edit mode.
When I run the program the textbox will take the value of the label that was in the ItemTemplate and I cant access the textbox.
.aspx:

<asp:GridView runat="server" ID="GridView1" AutoGenerateColumns="False"
ShowHeader="False" onrowcommand="GridView1_RowCommand"
onrowediting="GridView1_RowEditing" OnRowCancelingEdit="GridView1_Cancel" 
onrowupdating="GridView1_RowUpdating" onrowdeleting="GridView1_RowDeleting"
onrowdatabound="GridView1_RowDataBound" DataKeyNames="TweetID">
<Columns>
<asp:TemplateField HeaderText="ProfilePicture">
<ItemTemplate>
<asp:ImageButton ID="ProfileImage" runat="server" CommandName="Redirect" 
CommandArgument='<%# Container.DataItemIndex %>' Height="40px" Width="40px" />
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="FullName">
<ItemTemplate>
<asp:label ID="FullNameLabel" runat="server" text='<%#Eval("FullName") %>'></asp:label>
</ItemTemplate>
</asp:TemplateField>

<asp:TemplateField HeaderText="UserName">
<ItemTemplate>
<asp:Label ID="UserNameLabel" runat="server" Text='<%#Eval("UserName") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Tweet">
<ItemTemplate>
<%--<asp:Label ID="TweetLabel" runat="server" Text='<%#Eval("TweetText") %>'></asp:Label>--%>
<asp:Label ID="TweetLabel" runat="server" Text=""></asp:Label>
</ItemTemplate>

<EditItemTemplate>
<asp:TextBox ID="TweetTB" runat="server" Text='<%#Eval("TweetText") %>'></asp:TextBox>
</EditItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Picture">
<ItemTemplate>
<asp:Image ID="TweetPic" runat="server" 
ImageUrl='<%#"~/UploadedImages/"+Eval("PicName") %>' Height="125px" Width="222px" />
</ItemTemplate>
</asp:TemplateField>

<asp:TemplateField HeaderText="ReTweet">
<ItemTemplate>
<asp:ImageButton ID="ReTweetImgBTN" runat="server" 
ImageUrl="~/SrcImage/retweet-action.png" Height="27px" Width="29px" 
CommandName="ReTweet" CommandArgument='<%# Container.DataItemIndex %>'/>
<%--<asp:Label ID="ReTweetEd" runat="server" Text="ReTweetEd" Visible="false"></asp:Label>--%>
 <%--<asp:Button ID="ReTweetBTN" runat="server" Text="ReTweet"  CommandName="ReTweet" CommandArgument='<%# Container.DataItemIndex %>' />--%>
 <asp:Label ID="ReTweetStat" runat="server" Visible="false"></asp:Label>  
 </ItemTemplate>
 </asp:TemplateField>
<asp:TemplateField HeaderText="Like">
<ItemTemplate>
 <asp:ImageButton ID="LikeImgBTN" runat="server" ImageUrl="~/SrcImage/like-action.png"
 Height="27px" Width="29px" CommandName="Like" CommandArgument='<%# Container.DataItemIndex %>'/>
 <%--<asp:Button ID="LikeBTN" runat="server" Text="Like"  CommandName="Like" CommandArgument='<%# Container.DataItemIndex %>' />--%>
 <asp:Label ID="LikeStat" runat="server" Visible="false"></asp:Label>
  </ItemTemplate>
 </asp:TemplateField>

 <asp:TemplateField HeaderText="Options">  
 <ItemTemplate>  
 <asp:LinkButton ID="Edit" runat="server" Text="Edit" CommandName="Edit"  />
 </ItemTemplate>  
 <EditItemTemplate>  
 <asp:LinkButton ID="Delete" runat="server" Text="Delete" CommandName="Delete" />
 <asp:LinkButton ID="btn_Update" runat="server" Text="Update" CommandName="Update"/>
 <asp:LinkButton ID="btn_Cancel" runat="server" Text="Cancel" CommandName="Cancel"/>  
 </EditItemTemplate>  
 </asp:TemplateField>
 <asp:TemplateField HeaderText="TweetID" Visible="false">
 <ItemTemplate>
 <asp:HiddenField ID="TweetID" runat="server" Value='<%#Eval("TweetID") %>'  />
 </ItemTemplate>
 </asp:TemplateField>

 <asp:TemplateField HeaderText="UserID" Visible="false">
 <ItemTemplate>
 <asp:HiddenField ID="UserID" runat="server" Value='<%#Eval("UserID") %>'/>
 </ItemTemplate>
 </asp:TemplateField>

 </Columns>
 </asp:GridView>

.cs:

protected void Page_Load(object sender, EventArgs e)
    {
        Session["UserID"] = 1; // To be removed
        if(!IsPostBack)
            BindGridview();
    }
    protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        int userId = int.Parse(Session["UserID"].ToString());
        if (e.CommandName == "Like")
        {
            int index = Convert.ToInt32(e.CommandArgument);
            if (NewTweetHelper.IsTweetReTweetFromTweetByTweetId(int.Parse(GridView1.DataKeys[index].Value.ToString())))
            {
                int ReTweetID = NewTweetHelper.GetReTweetIDFromTweetByTweetID(int.Parse(GridView1.DataKeys[index].Value.ToString()));
                int tweetID = ReTweetHelper.GetTweetIDFromReTweetByReTweetID(ReTweetID);
                LikeHelper.Like(tweetID, userId);
            }
            else
                LikeHelper.Like(int.Parse(GridView1.DataKeys[index].Value.ToString()), userId);
        }
        if (e.CommandName == "ReTweet")
        {
            int index = Convert.ToInt32(e.CommandArgument);
            if (NewTweetHelper.IsTweetReTweetFromTweetByTweetId(int.Parse(GridView1.DataKeys[index].Value.ToString())))
            {
                int ReTweetID = NewTweetHelper.GetReTweetIDFromTweetByTweetID(int.Parse(GridView1.DataKeys[index].Value.ToString()));
                int tweetID = ReTweetHelper.GetTweetIDFromReTweetByReTweetID(ReTweetID);
                ReTweetHelper.ReTweet(tweetID, userId);
            }
            else
                ReTweetHelper.ReTweet(int.Parse(GridView1.DataKeys[index].Value.ToString()), userId);
        }
        if (e.CommandName == "UnReTweet")
        {
            int index = Convert.ToInt32(e.CommandArgument);
            int RetweetID = ReTweetHelper.GetReTweetIdFromReTweetByUserIdAndTweetId(int.Parse(GridView1.DataKeys[index].Value.ToString()), userId);
            int TweetID = NewTweetHelper.GetTweetIdFromTweetByReTweetId(RetweetID);
            ReTweetHelper.RemoveReTweet(RetweetID);
            NewTweetHelper.GeneralRemoveTweet(TweetID);
        }
        if (e.CommandName == "Redirect")
        {
            int index = Convert.ToInt32(e.CommandArgument);
            int TweetID = int.Parse(GridView1.DataKeys[index].Value.ToString());
            if (NewTweetHelper.IsTweetReTweetFromTweetByTweetId(TweetID))
            {
                int ReTweetID = NewTweetHelper.GetReTweetIDFromTweetByTweetID(TweetID);
                int RealTweetID = ReTweetHelper.GetTweetIDFromReTweetByReTweetID(ReTweetID);
                int UserID = NewTweetHelper.GetUserIdFromTweetByTweetId(RealTweetID);
                Response.Redirect("ProfilePage.aspx?UserName=" + UserHelper.GetUserName(UserID));
            }
            else
                Response.Redirect("ProfilePage.aspx?UserName=" + UserHelper.GetUserName(NewTweetHelper.GetUserIdFromTweetByTweetId(TweetID)));
        }
    }
    protected void GridView1_RowEditing(object sender, GridViewEditEventArgs e)
    {
        GridView1.EditIndex = e.NewEditIndex;
        GridView1.DataBind();
        //TextBox TextBox = GridView1.Rows[e.NewEditIndex].FindControl("TweetTB") as TextBox;
        //HiddenField TweetID = GridView1.Rows[e.NewEditIndex].FindControl("TweetID") as HiddenField;
        //TextBox.Text = NewTweetHelper.GetTweetFromTweetByTweetId(int.Parse(TweetID.Value.ToString())).TweetText;
    }
    protected void GridView1_Cancel(object sender, GridViewCancelEditEventArgs e)
    {
        GridView1.EditIndex = -1;
        GridView1.DataBind();
    }
    public void BindGridview()
    {
        int userId = int.Parse(Session["UserID"].ToString());
        ServiceReference1.WebServiceSoapClient objWs = new ServiceReference1.WebServiceSoapClient();
        DataSet ds = objWs.SelectTweets(userId, 0);
        DataTable dt = ds.Tables[0];
        GridView1.DataSource = dt;
        GridView1.DataBind();
    }
    protected void GridView1_RowDeleting(object sender, GridViewDeleteEventArgs e)
    {
        int userId = int.Parse(Session["UserID"].ToString());
        int index = Convert.ToInt32(e.RowIndex);
        if (NewTweetHelper.IsTweetReTweetFromTweetByTweetId(int.Parse(GridView1.DataKeys[index].Value.ToString())))
        {
            int RetweetID = NewTweetHelper.GetReTweetIDFromTweetByTweetID(int.Parse(GridView1.DataKeys[index].Value.ToString()));
            ReTweetHelper.RemoveReTweet(RetweetID);
            NewTweetHelper.GeneralRemoveTweet(int.Parse(GridView1.DataKeys[index].Value.ToString()));
        }
        else
            NewTweetHelper.GeneralRemoveTweet(Convert.ToInt32(GridView1.DataKeys[index].Value.ToString()));
    }
    protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        int userId = int.Parse(Session["UserID"].ToString());
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            HiddenField userIdLbl = (HiddenField)e.Row.FindControl("UserID");
            HiddenField tweetid = (HiddenField)e.Row.FindControl("TweetID");

            LinkButton editBt = (LinkButton)e.Row.FindControl("Edit");
            editBt.Visible = userId == Convert.ToInt32(userIdLbl.Value);

            ImageButton ProfileImage = e.Row.FindControl("ProfileImage") as ImageButton;
            ProfileImage.ImageUrl = "~/UploadedImages/" + UserHelper.GetImageUrl(int.Parse(userIdLbl.Value.ToString()));

            // if retweet
            if (NewTweetHelper.IsTweetReTweetFromTweetByTweetId(int.Parse(tweetid.Value.ToString())))
            {
                Tweet tweet = NewTweetHelper.GetTweetFromTweetByTweetId(int.Parse(tweetid.Value.ToString()));
                string FullName = UserHelper.GetName(tweet.UserID);
                // change tweet
                Label name = e.Row.FindControl("FullNameLabel") as Label;
                Label UserName = e.Row.FindControl("UserNameLabel") as Label;
                int ReTweetID = NewTweetHelper.GetReTweetIDFromTweetByTweetID(int.Parse(tweetid.Value.ToString()));
                int RealTweetID = ReTweetHelper.GetTweetIDFromReTweetByReTweetID(ReTweetID);
                int RealUserID = NewTweetHelper.GetUserIdFromTweetByTweetId(RealTweetID);
                name.Text = "Retweeted by " + FullName + "<br>" + UserHelper.GetName(RealUserID);
                UserName.Text = UserHelper.GetUserName(RealUserID);
                ProfileImage.ImageUrl = "~/UploadedImages/" + UserHelper.GetImageUrl(RealUserID);
                editBt.Visible = false;
            }

            //if there is image
            Image img = (Image)e.Row.FindControl("TweetPic");
            img.Visible = img.ImageUrl != "~/UploadedImages/";

            //stats
            Label LikeStat = e.Row.FindControl("LikeStat") as Label;
            Label ReTweetStat = e.Row.FindControl("ReTweetStat") as Label;
            if (NewTweetHelper.IsTweetReTweetFromTweetByTweetId(int.Parse(tweetid.Value.ToString())))
            {
                int ReTweetID = NewTweetHelper.GetReTweetIDFromTweetByTweetID(int.Parse(tweetid.Value.ToString()));
                int RealTweetID = ReTweetHelper.GetTweetIDFromReTweetByReTweetID(ReTweetID);
                LikeStat.Text = LikeHelper.AmountOfLikesByTweetId(RealTweetID).ToString();
                if (int.Parse(LikeStat.Text.ToString()) > 0)
                    LikeStat.Visible = true;
                ReTweetStat.Text = ReTweetHelper.AmountOfReTweets(RealTweetID).ToString();
                if (int.Parse(ReTweetStat.Text.ToString()) > 0)
                    ReTweetStat.Visible = true;
            }
            else
            {
                LikeStat.Text = LikeHelper.AmountOfLikesByTweetId(int.Parse(tweetid.Value.ToString())).ToString();
                if (int.Parse(LikeStat.Text.ToString()) > 0)
                    LikeStat.Visible = true;
                ReTweetStat.Text = ReTweetHelper.AmountOfReTweets(int.Parse(tweetid.Value.ToString())).ToString();
                if (int.Parse(ReTweetStat.Text.ToString()) > 0)
                    ReTweetStat.Visible = true;
            }

            // retweeted
            if (ReTweetHelper.IsReTweetExistByUserIdAndTweetId(userId,int.Parse(tweetid.Value.ToString())))
            {
                ImageButton Retweet = e.Row.FindControl("ReTweetImgBTN") as ImageButton;
                Retweet.ImageUrl = "~/SrcImage/retweet-action-on.png";
                Retweet.CommandName = "UnReTweet";
            }
            if (NewTweetHelper.IsTweetByUser(int.Parse(tweetid.Value.ToString()), userId)) 
            {
                ImageButton Retweet = e.Row.FindControl("ReTweetImgBTN") as ImageButton;
                Retweet.ImageUrl = "~/SrcImage/retweet-action-inactive.png";
                Retweet.CommandName = null;
            }

            //Like Button
            ImageButton LikeImg = e.Row.FindControl("LikeImgBTN") as ImageButton;
            if (NewTweetHelper.IsTweetReTweetFromTweetByTweetId(int.Parse(tweetid.Value.ToString())))
            {
                int ReTweetID = NewTweetHelper.GetReTweetIDFromTweetByTweetID(int.Parse(tweetid.Value.ToString()));
                int RealTweetID = ReTweetHelper.GetTweetIDFromReTweetByReTweetID(ReTweetID);
                if(LikeHelper.IsUserLikeTweet(userId,RealTweetID))    
                    LikeImg.ImageUrl = "~/SrcImage/like-action-on.png";
            }
            else
            {
                if (LikeHelper.IsUserLikeTweet(userId,int.Parse(tweetid.Value.ToString())))
                    LikeImg.ImageUrl = "~/SrcImage/like-action-on.png";

            }

            //Hyper Link Text

            Label TweetLabel = (Label)e.Row.FindControl("TweetLabel");
            //TextBox TweetTB = (TextBox)e.Row.FindControl("TweetTB");
            Tweet TweetText = NewTweetHelper.GetTweetFromTweetByTweetId(int.Parse(tweetid.Value.ToString()));
            //TweetTB.Text = "a";// TweetText.TweetText.ToString();
            string text = NewTweetHelper.HyperLinkTweet(int.Parse(tweetid.Value.ToString()));
            //TweetText.TweetText= text; //need?
            TweetLabel.Text = text;

            //Change Tb in edit cand do it in RowEditting
            //if (e.Row.RowState == DataControlRowState.Edit)
            //{
            //    TextBox TextBox = e.Row.FindControl("TweetTB") as TextBox;
            //    Tweet Text = NewTweetHelper.GetTweetFromTweetByTweetId(int.Parse(tweetid.Value.ToString()));
            //    TextBox.Text = "abc";
            //}

        }
    }
    protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        HiddenField TweetID = GridView1.Rows[e.RowIndex].FindControl("TweetID") as HiddenField;
        TextBox TweetText = GridView1.Rows[e.RowIndex].FindControl("TweetTB") as TextBox;
        NewTweetHelper.UpdateTweet(int.Parse(TweetID.Value), TweetText.Text);
        GridView1.EditIndex = -1;
        BindGridview();
    }

Answer 1

In the RowEditing event, you can set the EditIndex value and re-bind the data to the GridView:

protected void GridView1_RowEditing(object sender, GridViewEditEventArgs e)
{
    GridView1.EditIndex = e.NewEditIndex;
    BindGridView();
}

protected void GridView1_Cancel(object sender, GridViewCancelEditEventArgs e)
{
    GridView1.EditIndex = -1;
    BindGridView();
}

Then, in the RowDataBound event, you can access the controls of the row:

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowIndex == GridView1.EditIndex)
    {
        TextBox txtBox = e.Row.FindControl("TweetTB") as TextBox;
        ...
    }
    else
    {
        ...
    }
}