How to select data from database using a dropdownlist : The Official Microsoft ASP.NET Forums

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How to select data from database using a dropdownlist

Feb 19, 2012 12:10 PM|LINK

How to select data from database using a dropdownlist for this code block, instead of lastRecord.USD let the users select also lastRecord.EUR, lastRecord.GBP and lastRecord.CHF

@{
    var db = Database.Open("money");
    var lastRecord = db.QuerySingle("SELECT TOP 1 * FROM foreign ORDER BY ID DESC");
    
    var Result = 0m;
    
    if(IsPost) {
        
    var Price = decimal.Parse(lastRecord.USD);
        
    var UserInput = Request["UserInput"].AsDecimal();
        if (UserInput == 0) {
           ModelState.AddError("UserInput", "Enter amount!");
        }
        
    // calculate
    Result = UserInput * Price;
    }
}

    <form action="" method="post">

<table>
    <tr>
        <td> // use here a select dropdownlist //</td>
        <td><input type="text" name="UserInput" size="14" value="1"/></td>
    </tr>
</table>
        
     </form>
    
    <text>Result: @Result</text>

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Re: How to select data from database using a dropdownlist

Feb 19, 2012 01:41 PM|LINK

You can refer to a lastRecord column with this syntax:

lastRecord[columnName]

so you can use a dropdown list as this one:

<select name="currency">
    <option>USD</option>
    <option>EUR</option>
    <option>GBP</option>
    <option>CHF</option>
</select>

and replace the row

var Price = decimal.Parse(lastRecord.USD);

with

var Price = decimal.Parse(lastRecord[Request["currency"]]);

Edited by GmGregori on Feb 19, 2012 01:42 PM
Edited by GmGregori on Feb 19, 2012 01:43 PM
Marked as answer by dow7 on Feb 19, 2012 02:45 PM

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Re: How to select data from database using a dropdownlist

Feb 19, 2012 02:46 PM|LINK

Thank you,

is there a way to keep the selected option after the submit?

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Re: How to select data from database using a dropdownlist

Feb 19, 2012 10:18 PM|LINK

Maybe you could do all the work in client side with jQuery in a page like this one:

@{
    var db = Database.Open("money");
    var lastRecord = db.QuerySingle("SELECT TOP 1 * FROM foreign ORDER BY ID DESC");
}
 
<head>
	<script src="@Href("~/Scripts/jquery-1.6.2.min.js")" type="text/javascript"></script>
</head>
<div>
	<select name="currency" id="currency">
		<option value="0">Select</option>
		<option value="@lastRecord.USD">USD</option>
		<option value="@lastRecord.EUR">EUR</option>
		<option value="@lastRecord.GBP">GBP</option>
		<option value="@lastRecord.CHF">CHF</option>
	</select>
	<input type="text" id="UserInput" size="14" value="1"/>
	<input type="text" id="Result" size="14" value="0"/>
</div>

<script>
    $('#currency').change(performVal);
    
    function performVal() {
        var amount = parseFloat($('#UserInput').val());
        var rate = parseFloat($("#currency").val());
        var result = amount * rate;
        $('#Result').val(result);
    }
</script>

Pay attention to the jQuery library link.

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Re: How to select data from database using a dropdownlist

Feb 21, 2012 03:48 PM|LINK

Thank you a lot,

two more questions, how to avoid the error message if the user leave the option 0 (<option value="0">Select</option>)? Instead use something like this code, but for the list because i get error:Invalid column name :

var UserInput = Request["UserInput"].AsDecimal();
if (UserInput == 0) {
ModelState.AddError("UserInput", "Enter amount!");
}

and how to display the Result after the submit, (for the code below)

@{
    var db = Database.Open("money");
    var lastRecord = db.QuerySingle("SELECT TOP 1 * FROM foreign ORDER BY ID DESC");
    
    var Result = 0m;
    var LastValue = Request["UserInput"];
    var LastPrice = Request["currency"];
    
    if(IsPost) {
        
    var Price = decimal.Parse(lastRecord[Request["currency"]]);
        
        
    var UserInput = Request["UserInput"].AsDecimal();
        if (UserInput == 0) {
           ModelState.AddError("UserInput", "Enter amount!");
        }
        
    // calculate
    Result = UserInput * Price;
    }
}

    
    
    
    <form action="" method="post">

<table>
    <tr>
        <td><select name="currency">
    <option>Select</option>
    <option>USD</option>
    <option>EUR</option>
    <option>GBP</option>
    <option>CHF</option>
    <option>JPY</option>
</select></td>
        </tr>
    <tr>
        <td><input type="text" name="UserInput" size="14" value="1"/> <input type="submit" value="Go"/></td>
        
    </tr>
</table>
        
     </form>
    
    <text>@if(ModelState.IsValid) {<span>Result:</span> @LastValue<span>&nbsp;</span>@LastPrice @Result} else {@Html.ValidationSummary()}</text>

Edited by dow7 on Feb 21, 2012 03:50 PM
Edited by dow7 on Feb 21, 2012 03:50 PM
Edited by dow7 on Feb 21, 2012 04:03 PM

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GmGregori

Contributor

5574 Points

749 Posts

Re: How to select data from database using a dropdownlist

Feb 22, 2012 12:48 PM|LINK

I'm not sure to understand what you mean.

dow7
how to avoid the error message if the user leave the option 0 (<option value="0">Select</option>)? Instead use something like this code, but for the list because i get error:Invalid column name

The option 0 (<option value="0">Select</option>) it's needed in my example using jQuery, because the result is displayed when the user makes a selection in the dropdown list.

Otherwise it's not needed: the first row (USD?) is selected by itself and the user can accept or change it before to click the "Go" button.

For the second question, the last row of your code formats the result layout

<span>Result:</span> @LastValue<span>&nbsp;</span>@LastPrice @Result

and you get something like: Result: 1 USD0.045

In your code there are some unnecessary span tags, but, apart from that, you can format the output as you prefer.

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dow7

Member

738 Points

452 Posts

Re: How to select data from database using a dropdownlist

Feb 23, 2012 03:54 PM|LINK

i mean for the code above (http://forums.asp.net/post/4843467.aspx) without javascript, i leave the option 0 (<option value="0">Select</option>).

So, i want to add a ModelState.AddError for this option, if the user leave option 0.

Its something like this example but is not as AsInt, is as AsDecmial

if (Request["employees"].IsInt()) {
            employeecount = Request["employees"].AsInt();
        } else {
            errors = true;
            @:Employee count must be a number.<br />
        }

Edited by dow7 on Feb 23, 2012 04:00 PM
Edited by dow7 on Feb 23, 2012 04:02 PM

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GmGregori

Contributor

5574 Points

749 Posts

Re: How to select data from database using a dropdownlist

Feb 23, 2012 07:35 PM|LINK

Try the code that follows:

@{
    var db = Database.Open("money");
    var lastRecord = db.QuerySingle("SELECT TOP 1 * FROM foreign ORDER BY ID DESC");
     
    var Result = 0m;
    var Price = 0m;
    var LastValue = Request["UserInput"];
    var LastPrice = Request["currency"];
     
    if(IsPost) {
        
        if (LastPrice != "Select") {
            Price = decimal.Parse(lastRecord[LastPrice]);
        } else {
            ModelState.AddError("Price", "Select currency!");
        }
         
        var UserInput = Request["UserInput"].AsDecimal();
        if (UserInput == 0) {
            ModelState.AddError("UserInput", "Enter amount!");
        }
         
        // calculate
        if (ModelState.IsValid) {
            Result = UserInput * Price;
        }
    }
}

Marked as answer by dow7 on Feb 23, 2012 08:58 PM

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dow7

How to select data from database using a dropdownlist

GmGregori

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dow7

Re: How to select data from database using a dropdownlist

GmGregori

Re: How to select data from database using a dropdownlist

dow7

Re: How to select data from database using a dropdownlist

GmGregori

Re: How to select data from database using a dropdownlist

dow7

dow7

Re: How to select data from database using a dropdownlist

GmGregori

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