Calculate Debit and Credit based on ASP.Net TextBox value using C#

Hi smile,

As the ddltype list item text has space at starting and ending, your if condition is not sartisfying. You need to trim the space for comparing the text.

Refer below sample.

HTML

<div class="container-fluid">
    <div class="row">
        <div class="col-sm-3">
            <label class="control-label" style="margin-top: 10px;">
                Type</label>
            <asp:DropDownList ID="ddlType" runat="server"
                class="validate[required] form-control" AutoPostBack="true"
                OnSelectedIndexChanged="ddlType_SelectedIndexChanged">
                <asp:ListItem> ---Select One--- </asp:ListItem>
                <asp:ListItem> Credit </asp:ListItem>
                <asp:ListItem> Debit </asp:ListItem>
            </asp:DropDownList>
        </div>
        <div class="col-sm-3">
            <label class="control-label" style="margin-top: 10px;">
                Select Account
            </label>
            <asp:DropDownList ID="ddlAcc" runat="server" class="validate[required] form-control">
            </asp:DropDownList>
        </div>
        <div class="col-sm-3">
            <label class="control-label" style="margin-top: 10px;">
                Balance
            </label>
            <asp:TextBox ID="txtPay" runat="server" class="form-control" Text="0"></asp:TextBox>
        </div>
    </div>
    <div class="row">
        <div class="col-sm-3">
            <label class="control-label" style="margin-top: 10px;">
                Amount</label>
            <asp:TextBox ID="txtCredit" runat="server" class="form-control" Text="0"
                OnTextChanged="txtCredit_TextChanged" AutoPostBack="true"></asp:TextBox>
        </div>
        <div class="col-sm-3">
            <label class="control-label" style="margin-top: 10px;">
                Total Balance
            </label>
            <asp:TextBox ID="txtDesc" runat="server" class="form-control" placeholder="Description"></asp:TextBox>
        </div>
    </div>
</div>

Code

protected void txtCredit_TextChanged(object sender, EventArgs e)
{
    this.CalculatBalance();
}

protected void ddlType_SelectedIndexChanged(object sender, EventArgs e)
{
    this.CalculatBalance();
}

private void CalculatBalance()
{
    double amount = Convert.ToInt64(txtPay.Text);
    double credit = Convert.ToInt64(txtCredit.Text);
    double balance = 0;
    if (ddlType.SelectedItem.Value.ToString().Trim().ToLower() == "credit")
    {
        balance = Convert.ToInt64(amount + credit);
    }
    if (ddlType.SelectedItem.Text.ToString().Trim().ToLower() == "debit")
    {
        balance = Convert.ToInt64(amount - credit);
    }
    txtDesc.Text = balance.ToString();
}

Screenshot