Calculate and validate Total amount with TextBox and Repeater Item value in ASP.Net

Hi yati,

PLease refer below code and chenge your code.

HTML

<div>
    DonationAmount :
    <asp:TextBox ID="txtDonationAmount" runat="server" class="form-control  input-sm"></asp:TextBox>
    <br />
    From :
    <asp:TextBox ID="txtReceiveFrom" runat="server" CssClass="form-control input-sm"></asp:TextBox>
    Amount Given:
    <asp:TextBox ID="txtAmountgiven" runat="server" CssClass="form-control input-sm"></asp:TextBox>
    <br />
    <asp:Button ID="btnAddReceipt" runat="server" Text="Add Receipt Detail" OnClick="btnAddReceipt_Click" />
    <hr />
    <asp:Repeater ID="RPT_RCTP_DTL" runat="server">
        <ItemTemplate>
            <table>
                <tr>
                    <td>
                        <asp:Label ID="lblPayType" Text='<%# Eval("Person")%>' runat="server"></asp:Label>
                    </td>
                    <td>
                        <asp:Label ID="Label1" Text='<%# Eval("Amount")%>' runat="server"></asp:Label>
                    </td>
                </tr>
            </table>
        </ItemTemplate>
    </asp:Repeater>
    <asp:Button ID="btnSave" runat="server" CssClass="btn btn-primary" Text="Save" OnClick="btnsave_Click">
    </asp:Button>
</div>

Namespaces

C#

using System.Data;

VB.Net

Imports System.Data

Code

C#

DataTable dt = new DataTable();
protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        dt.Columns.AddRange(new DataColumn[] { new DataColumn("Person", typeof(string)), new DataColumn("Amount", typeof(int)) });
        RPT_RCTP_DTL.DataSource = dt;
        RPT_RCTP_DTL.DataBind();
        Session["dt"] = dt;
    }
}

protected void btnAddReceipt_Click(object sender, EventArgs e)
{
    int amountDonation = int.Parse(txtDonationAmount.Text);
    int amountReceive = int.Parse(txtAmountgiven.Text);
    dt = (DataTable)Session["dt"];
    DataRow dr = dt.NewRow();
    dr["Person"] = txtReceiveFrom.Text;
    dr["Amount"] = txtAmountgiven.Text;
    int sum = dt.Rows.Count > 0 ? Convert.ToInt32(dt.Compute("SUM(Amount)", string.Empty)) : 0;
    int tot = sum + amountReceive;
    if (amountDonation < amountReceive)
    {
        string message = "alert('Amount Exceeded')";
        ScriptManager.RegisterClientScriptBlock((sender as Control), this.GetType(), "alert", message, true);
    }
    else if (amountDonation < tot)
    {
        string message = "alert('Amount Exceeded')";
        ScriptManager.RegisterClientScriptBlock((sender as Control), this.GetType(), "alert", message, true);
    }
    else
    {
        if (amountReceive > 0)
        {
            dt.Rows.Add(dr);
            RPT_RCTP_DTL.DataSource = dt;
            RPT_RCTP_DTL.DataBind();
        }
    }
}

protected void btnsave_Click(object sender, EventArgs e)
{ 
    dt = Session["dt"] as DataTable;
    int sum = dt.Rows.Count > 0 ? Convert.ToInt32(dt.Compute("SUM(Amount)", string.Empty)) : 0;
    int amountDonation = int.Parse(txtDonationAmount.Text);
    if (sum > amountDonation)
    {
        string message = "alert('Amount Exceeded')";
        ScriptManager.RegisterClientScriptBlock((sender as Control), this.GetType(), "alert", message, true);
    }
}

 VB.Net

Private dt As DataTable = New DataTable()
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        dt.Columns.AddRange(New DataColumn() {New DataColumn("Person", GetType(String)), New DataColumn("Amount", GetType(Integer))})
        RPT_RCTP_DTL.DataSource = dt
        RPT_RCTP_DTL.DataBind()
        Session("dt") = dt
    End If
End Sub

Protected Sub btnAddReceipt_Click(ByVal sender As Object, ByVal e As EventArgs)
    Dim amountDonation As Integer = Integer.Parse(txtDonationAmount.Text)
    Dim amountReceive As Integer = Integer.Parse(txtAmountgiven.Text)
    dt = CType(Session("dt"), DataTable)
    Dim dr As DataRow = dt.NewRow()
    dr("Person") = txtReceiveFrom.Text
    dr("Amount") = txtAmountgiven.Text
    Dim sum As Integer = If(dt.Rows.Count > 0, Convert.ToInt32(dt.Compute("SUM(Amount)", String.Empty)), 0)
    Dim tot As Integer = sum + amountReceive

    If amountDonation < amountReceive Then
        Dim message As String = "alert('Amount Exceeded')"
        ScriptManager.RegisterClientScriptBlock((TryCast(sender, Control)), Me.[GetType](), "alert", message, True)
    ElseIf amountDonation < tot Then
        Dim message As String = "alert('Amount Exceeded')"
        ScriptManager.RegisterClientScriptBlock((TryCast(sender, Control)), Me.[GetType](), "alert", message, True)
    Else

        If amountReceive > 0 Then
            dt.Rows.Add(dr)
            RPT_RCTP_DTL.DataSource = dt
            RPT_RCTP_DTL.DataBind()
        End If
    End If
End Sub

Protected Sub btnsave_Click(ByVal sender As Object, ByVal e As EventArgs)
    dt = TryCast(Session("dt"), DataTable)
    Dim sum As Integer = If(dt.Rows.Count > 0, Convert.ToInt32(dt.Compute("SUM(Amount)", String.Empty)), 0)
    Dim amountDonation As Integer = Integer.Parse(txtDonationAmount.Text)

    If sum > amountDonation Then
        Dim message As String = "alert('Amount Exceeded')"
        ScriptManager.RegisterClientScriptBlock((TryCast(sender, Control)), Me.[GetType](), "alert", message, True)
    End If
End Sub