Get TextBox value of each GridView row on Button click in ASP.Net

Here I have created sample for you in that  GridView takes hobbies and display it on Label on Button click.

HTML

<div>
<cc1:ToolkitScriptManager runat="server">
</cc1:ToolkitScriptManager>
<asp:Button ID="btnShowDetails" Text="Show Details" runat="server" />
<asp:Panel ID="pnlDeatils" runat="server" Style="display: none" CssClass="modalPopup">
    <asp:GridView ID="gvDetails" HeaderStyle-BackColor="#3AC0F2" HeaderStyle-ForeColor="White"
        runat="server" AutoGenerateColumns="false">
        <Columns>
            <asp:BoundField DataField="Id" HeaderText="Id" ItemStyle-Width="30" />
            <asp:BoundField DataField="Name" HeaderText="Name" ItemStyle-Width="150" />
            <asp:BoundField DataField="Country" HeaderText="Country" ItemStyle-Width="150" />
            <asp:TemplateField>
                <ItemTemplate>
                    <asp:TextBox ID="txtHobby" runat="server" />
                </ItemTemplate>
            </asp:TemplateField>
        </Columns>
    </asp:GridView>
    <br />
    <asp:Button ID="btnHobbies" Text="ShowHobbies" runat="server" OnClick="ShowHobbies" />
</asp:Panel>
<cc1:ModalPopupExtender ID="mpe" runat="server" TargetControlID="btnShowDetails"
    PopupControlID="pnlDeatils" BackgroundCssClass="modalBackground">
</cc1:ModalPopupExtender>
<br />
<asp:Label ID="lblHobbies" runat="server" />
</div>

C#

Namespace

using System.Data;

Code

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dt = new DataTable();
        dt.Columns.AddRange(new DataColumn[3] { new DataColumn("Id", typeof(int)),
                        new DataColumn("Name", typeof(string)),
                        new DataColumn("Country",typeof(string)) });
        dt.Rows.Add(1, "John Hammond", "United States");
        dt.Rows.Add(2, "Mudassar Khan", "India");
        dt.Rows.Add(3, "Suzanne Mathews", "France");
        dt.Rows.Add(4, "Robert Schidner", "Russia");
        gvDetails.DataSource = dt;
        gvDetails.DataBind();
    }
}

protected void ShowHobbies(object sender, EventArgs e)
{
    string hobbies = string.Empty;
    foreach (GridViewRow row in gvDetails.Rows)
    {
        TextBox txthobby = (TextBox)row.FindControl("txtHobby");
        hobbies += txthobby.Text + ", ";
    }
    lblHobbies.Text = "Hobbies are " + hobbies;
}

VB

Namespace

Imports System.Data

Code

Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim dt As New DataTable()
        dt.Columns.AddRange(New DataColumn(2) {New DataColumn("Id", GetType(Integer)), New DataColumn("Name", GetType(String)), New DataColumn("Country", GetType(String))})
        dt.Rows.Add(1, "John Hammond", "United States")
        dt.Rows.Add(2, "Mudassar Khan", "India")
        dt.Rows.Add(3, "Suzanne Mathews", "France")
        dt.Rows.Add(4, "Robert Schidner", "Russia")
        gvDetails.DataSource = dt
        gvDetails.DataBind()
    End If
End Sub

Protected Sub ShowHobbies(sender As Object, e As EventArgs)
    Dim hobbies As String = String.Empty
    For Each row As GridViewRow In gvDetails.Rows
        Dim txthobby As TextBox = DirectCast(row.FindControl("txtHobby"), TextBox)
        hobbies += txthobby.Text + ", "
    Next
    lblHobbies.Text = Convert.ToString("Hobbies are ") & hobbies
End Sub