Set Summer Note TextBox on GridView Row selection using C# and VB.Net

Hi ramco1917,

Please refer below sample.

HTML

<asp:GridView ID="gvCustomers" runat="server" AutoGenerateColumns="false">
    <Columns>
        <asp:BoundField HeaderText="CustomerId" DataField="CustomerId" />
        <asp:BoundField HeaderText="Name" DataField="Name" />
        <asp:BoundField HeaderText="Country" DataField="Country" />
        <asp:TemplateField>
            <ItemTemplate>
                <asp:Button ID="btnView" Text="View" runat="server" OnClientClick="BindData(this)" />
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>
<div class="col-lg-12">
    <div class="form-group">
        <asp:HiddenField ID="hfID" runat="server" />
        <label>Name</label>&nbsp;<span style="color: red">*</span>
        <asp:TextBox ID="txtName" runat="server" TextMode="MultiLine" Rows="2" class="summernote"></asp:TextBox>
    </div>
</div>
<link href="https://stackpath.bootstrapcdn.com/bootstrap/3.4.1/css/bootstrap.min.css" rel="stylesheet" />
<script src="https://code.jquery.com/jquery-3.5.1.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/3.4.1/js/bootstrap.min.js"></script>
<link href="https://cdn.jsdelivr.net/npm/summernote@0.8.18/dist/summernote.min.css" rel="stylesheet" />
<script src="https://cdn.jsdelivr.net/npm/summernote@0.8.18/dist/summernote.min.js"></script>
<script type="text/javascript">
    function BindData(e) {
        var currentRow = $(e).closest("tr");
        var id = currentRow.find("td:eq(0)").text();
        var name = currentRow.find("td:eq(1)").text();
        document.getElementById('<%=hfID.ClientID%>').value = id;
        document.getElementById('<%=txtName.ClientID%>').value = name;
    };
    $(function () {
        $('.summernote').summernote();
    });
</script>

Namespaces

C#

using System.Configuration;
using System.Data.SqlClient;

VB.Net

Imports System.Configuration
Imports System.Data.SqlClient

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if(!this.IsPostBack)
    {
        this.GridViewBind();
    }
}
private void GridViewBind()
{
    string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using(SqlConnection con = new SqlConnection(conString))
    {
        using(SqlCommand cmd = new SqlCommand("SELECT CustomerId, Name, Country FROM Customers", con))
        {
            con.Open();
            gvCustomers.DataSource = cmd.ExecuteReader();
            gvCustomers.DataBind();
            con.Close();
        }
    }
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Me.GridViewBind()
    End If
End Sub

Private Sub GridViewBind()
    Dim conString As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(conString)
        Using cmd As SqlCommand = New SqlCommand("SELECT CustomerId, Name, Country FROM Customers", con)
            con.Open()
            gvCustomers.DataSource = cmd.ExecuteReader()
            gvCustomers.DataBind()
            con.Close()
        End Using
    End Using
End Sub

Screenshot