How to increment a value on Button Click in ASP.Net

Ref:Persist Data / Object / Variable values across PostBack in ASP.Net

Values of the local variable can be lost during postback so you have to use ViewState.

Set the count value in ViewState.

ViewState("Count") = counter

Before increasing the counter value you need to check the ViewState value and again assign the value to ViewState.

If ViewState("Count") IsNot Nothing Then
	counter = Convert.toInt32(ViewState("Count"))
End If
counter = counter + 1
ViewState("Count") = counter

Example:

Here i will increament the counter value on ButtonClick

HTML:

<form id="form1" runat="server">
<div>
    <asp:Label ID="lblCount" runat="server" />
    <asp:Button Text="Increament counter" OnClick="IncreamentCounter" runat="server" />
</div>
</form>

C#:

protected void IncreamentCounter(object sender, EventArgs e)
{
    int counter;
    if (ViewState["Count"] != null)
    {
        counter = Convert.ToInt32(ViewState["Count"]);
    }
    else
    {
        counter = 0;
    }
    counter = counter + 1;
    ViewState["Count"] = counter;
    this.lblCount.Text = counter.ToString();
}

VB:

Protected Sub IncreamentCounter(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click

    Dim counter As Integer
    If ViewState("Count") IsNot Nothing Then
        counter = Convert.ToInt32(ViewState("Count"))
    Else
        counter = 0
    End If
    counter = counter + 1
    ViewState("Count") = counter
    Me.lblCount.Text = counter.ToString()
End Sub

Thank You.