How to filter GridView Based on Dynamically Added Textboxes on first row position using C# and VB.Net in ASP.Net

Hi Ruben12345,

I have created sample code which fulfill your requirement.

HTML

<div>
    <asp:GridView ID="gvCustomers" AutoGenerateColumns="true" runat="server" EmptyDataText="No Records Found"
        OnDataBound="gvCustomers_DataBound" />
    <br />
    <asp:Button ID="Button1" Text="SHOW ALL" OnClick="onclick" runat="server" />
</div>

C#

string constring = ConfigurationManager.ConnectionStrings["constr"].ToString();
int customerId = 0;
string Name;
string country;
protected void Page_Load(object sender, EventArgs e)
{
    this.GetData();
}

private void GetData()
{
    SqlConnection con = new SqlConnection(constring);
    SqlCommand cmd = new SqlCommand("SELECT * from Customers", con);
    SqlDataAdapter sda = new SqlDataAdapter(cmd);
    DataTable dt = new DataTable();
    sda.Fill(dt);
    gvCustomers.DataSource = dt;
    gvCustomers.DataBind();
}

protected void gvCustomers_DataBound(object sender, EventArgs e)
{
    GridViewRow row = new GridViewRow(0, 0, DataControlRowType.Header, DataControlRowState.Normal);
    for (int i = 0; i <= gvCustomers.HeaderRow.Cells.Count - 1; i++)
    {
        TableHeaderCell cell = new TableHeaderCell();
        TextBox txtsearch = new TextBox();
        txtsearch.Attributes["Placeholder"] = gvCustomers.HeaderRow.Cells[i].Text;
        txtsearch.ID = "txt-" + gvCustomers.HeaderRow.Cells[i].Text;
        txtsearch.CssClass = "textbox";
        txtsearch.TextChanged += new EventHandler(txtsearch_TextChanged);
        txtsearch.AutoPostBack = true;
        txtsearch.EnableViewState = true;
        cell.Controls.Add(txtsearch);
        row.Controls.Add(cell);
    }

    gvCustomers.HeaderRow.Parent.Controls.AddAt(1, row);
}

protected void txtsearch_TextChanged(object sender, EventArgs e)
{
    SqlConnection con = new SqlConnection(constring);
    GridViewRow row = ((sender as TextBox).NamingContainer as GridViewRow);
    string HeaderName = ((System.Web.UI.Control)(sender)).ID.Split('-')[1];
    switch (HeaderName.ToUpper())
    {
        case "CUSTOMERID":
            customerId = Convert.ToInt32((row.FindControl("txt-" + HeaderName + "") as TextBox).Text.Trim());
            break;

        case "NAME":
            Name = (row.FindControl("txt-" + HeaderName + "") as TextBox).Text.Trim();
            break;

        case "COUNTRY":
            country = (row.FindControl("txt-" + HeaderName + "") as TextBox).Text.Trim();
            break;

        default:
            break;
    }

    string query = "SELECT [CustomerID],[Name],[Country] FROM [Customers]";
    string whereCondition = string.Empty;
    if (customerId > 0)
    {
        whereCondition = "CustomerId ='" + customerId + "'";
    }

    if (!string.IsNullOrEmpty(Name))
    {
        if (!string.IsNullOrEmpty(whereCondition))
        {
            whereCondition += "And Name LIKE '%" + Name + "%'";
        }
        else
        {
            whereCondition += "Name LIKE '%" + Name + "%'";
        }
    }

    if (!string.IsNullOrEmpty(country))
    {
        if (!string.IsNullOrEmpty(whereCondition))
        {
            whereCondition += "And Country LIKE '%" + country + "%'";
        }
        else
        {
            whereCondition += "Country LIKE '%" + country + "%'";
        }
    }

    whereCondition = !string.IsNullOrEmpty(whereCondition) ? " WHERE " + whereCondition : whereCondition;
    query += whereCondition;
    using (SqlCommand cmd = new SqlCommand(query, con))
    {
        SqlDataAdapter sda = new SqlDataAdapter(cmd);
        DataTable dt = new DataTable();
        sda.Fill(dt);
        gvCustomers.DataSource = dt;
        gvCustomers.DataBind();
    }
}

protected void onclick(object sender, EventArgs e)
{
    this.GetData();
}

Vb.net

Private constring As String = ConfigurationManager.ConnectionStrings("constr").ToString()
Private customerId As Integer = 0
Private Name As String
Private country As String
Protected Sub Page_Load(sender As Object, e As EventArgs)
	Me.GetData()
End Sub

Private Sub GetData()
	Dim con As New SqlConnection(constring)
	Dim cmd As New SqlCommand("SELECT * from Customers", con)
	Dim sda As New SqlDataAdapter(cmd)
	Dim dt As New DataTable()
	sda.Fill(dt)
	gvCustomers.DataSource = dt
	gvCustomers.DataBind()
End Sub

Protected Sub gvCustomers_DataBound(sender As Object, e As EventArgs)
	Dim row As New GridViewRow(0, 0, DataControlRowType.Header, DataControlRowState.Normal)
	For i As Integer = 0 To gvCustomers.HeaderRow.Cells.Count - 1
		Dim cell As New TableHeaderCell()
		Dim txtsearch As New TextBox()
		txtsearch.Attributes("Placeholder") = gvCustomers.HeaderRow.Cells(i).Text
		txtsearch.ID = "txt-" + gvCustomers.HeaderRow.Cells(i).Text
		txtsearch.CssClass = "textbox"
		txtsearch.TextChanged += New EventHandler(AddressOf txtsearch_TextChanged)
		txtsearch.AutoPostBack = True
		txtsearch.EnableViewState = True
		cell.Controls.Add(txtsearch)
		row.Controls.Add(cell)
	Next

	gvCustomers.HeaderRow.Parent.Controls.AddAt(1, row)
End Sub

Protected Sub txtsearch_TextChanged(sender As Object, e As EventArgs)
	Dim con As New SqlConnection(constring)
	Dim row As GridViewRow = TryCast(TryCast(sender, TextBox).NamingContainer, GridViewRow)
	Dim HeaderName As String = DirectCast(sender, System.Web.UI.Control).ID.Split("-"C)(1)
	Select Case HeaderName.ToUpper()
		Case "CUSTOMERID"
			customerId = Convert.ToInt32(TryCast(row.FindControl((Convert.ToString("txt-") & HeaderName) + ""), TextBox).Text.Trim())
			Exit Select

		Case "NAME"
			Name = TryCast(row.FindControl((Convert.ToString("txt-") & HeaderName) + ""), TextBox).Text.Trim()
			Exit Select

		Case "COUNTRY"
			country = TryCast(row.FindControl((Convert.ToString("txt-") & HeaderName) + ""), TextBox).Text.Trim()
			Exit Select
		Case Else

			Exit Select
	End Select

	Dim query As String = "SELECT [CustomerID],[Name],[Country] FROM [Customers]"
	Dim whereCondition As String = String.Empty
	If customerId > 0 Then
		whereCondition = "CustomerId ='" + customerId + "'"
	End If

	If Not String.IsNullOrEmpty(Name) Then
		If Not String.IsNullOrEmpty(whereCondition) Then
			whereCondition += (Convert.ToString("And Name LIKE '%") & Name) + "%'"
		Else
			whereCondition += (Convert.ToString("Name LIKE '%") & Name) + "%'"
		End If
	End If

	If Not String.IsNullOrEmpty(country) Then
		If Not String.IsNullOrEmpty(whereCondition) Then
			whereCondition += (Convert.ToString("And Country LIKE '%") & country) + "%'"
		Else
			whereCondition += (Convert.ToString("Country LIKE '%") & country) + "%'"
		End If
	End If

	whereCondition = If(Not String.IsNullOrEmpty(whereCondition), Convert.ToString(" WHERE ") & whereCondition, whereCondition)
	query += whereCondition
	Using cmd As New SqlCommand(query, con)
		Dim sda As New SqlDataAdapter(cmd)
		Dim dt As New DataTable()
		sda.Fill(dt)
		gvCustomers.DataSource = dt
		gvCustomers.DataBind()
	End Using
End Sub

Protected Sub onclick(sender As Object, e As EventArgs)
	Me.GetData()
End Sub

Screenshot