How can I solved system.invalidcastexception was unhandled?

sigfredo santiago

10y2.9k

I have a WPF DataGrid to display PostgreSQL data. It displays a data table with 14 rows. It is an external connection to server and the number of columns change constantly depending on the user parameters. I have created a class called UCS1freqs and I use it to set the frequency values from data for later plotting those values into a scatter chart. The problem is that once it collects all the data it gives me a invalid cast Exception was unhandled (Unable to cast object of type MS.Internal.NamedObject to type System.Data.DataRowView). I know the problem is related to me using DataRowView. I'm new to code and definitely new to WPF. Any help is greatly appreciated

var ucs1Freqs = new List<Ucs1Freq>();

foreach (DataRowView row in DataGrid1.Items)

{

If (Convert.ToDouble(row.Row.ItemArray[11]) == 28.464258839)

{

var Ucs1freqstring = row.Row.ItemArray[0].ToString();

row.Row.ItemArray[0] = Ucs1freqstring;

Ucs1Freq tempFreq = new Ucs1Freq();

tempFreq.Frequency = Ucs1freqstring;

ucs1Freqs.Add(tempFreq);

}

6 Replies

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Tapan Patel10y ago
I think it is not possible to convert this way, instead there are other ways to handle/iterate over the datagrid in wpf.
such as
Foreach(classname classobject in datagrid.Items/datagrid.itemssource)
{
// do the operation here.... Each classobject represents a row on datagrid in wpf
}

Please consider other options. Also, DataRowView cannot be used on enumerator.
Nitin Sontakke10y ago
Unfortunately, I have never used WPF. However, the fundamentals are same across all technologies. You will need to refer to following page (documentation) on DataGrid in WPF:
https://msdn.microsoft.com/en-us/library/system.windows.controls.datagrid(v=vs.110).aspx
I don't think it is as straight forward as you are doing it.
My impression (note this word, i have no knowledge) is the grid has collection of controls and controls in turn have values. You will need to get access to the control first and then it's value. That's what i think.
sigfredo santiago10y ago
the error is happeningin this line
foreach (DataRowView row in DataGrid1.Items)
specifically at"row"
thanks
Nitin Sontakke10y ago
I just guessed the line, which MIGHT be giving error. If you give more exception details and line which giving the error that would be helpful. Hope the line is in there in code already shared by you.
Basically, all you have to do is, manage data types. Also avoid var and make it data type if you already know.
sigfredo santiago10y ago
Thank you for the suggestions. Ichanged the code, but still getting same error. I'm also including the class properties here. Thanks
class Ucs1Freq

{

private double _frequency;

public double Frequency

{

get { return _frequency; }

set { _frequency = value; }

}

}
//change in code, same error
var ucs1Freqs = new List<Ucs1Freq>();

foreach (DataRowView row in DataGrid1.Items)

{

if (Convert.ToDouble(row.Row.ItemArray[11]) == 28.464258839)

{

var Ucs1freqstring = row.Row.ItemArray[0];

row.Row.ItemArray[0] = Ucs1freqstring;

Ucs1Freq tempFreq = new Ucs1Freq();

tempFreq.Frequency = (double)Ucs1freqstring;

ucs1Freqs.Add(tempFreq);

}

}
Nitin Sontakke10y ago
You have not shown the class code forUcs1Freq. In any case, what is the data-type of the Frequency property. You will need to cast the Ucs1freqstring variable to that data type.
So, for example, it is double, then you will need to write as follows:
tempFreq.Frequency = (double) Ucs1freqstring;
Even better, just try removing .ToString()
Hope it helps!