We Keep Coding

unable to cast object of type 'System.Int32' to type 'System.String'. and also keep getting error Input string was not in a correct format

need help to resolve this error please can someone correct this up? i've commented the line in below code
discount = Conversion.Val(Dt.Rows[indx]["DiscountRate"]);
subtotal = (int) ((days * rate) - ((days * rate) * discount));
*total = System.Convert.ToInt32(((Conversion.Val(subtotal.ToString()) - Conversion.Val(Dt.Rows[indx]["AdvancePayment"].ToString())).ToString("00.00")));*//Input string was not in a correct format.
if (Conversion.Val(subtotal.ToString()) > Conversion.Val(Dt.Rows[indx]["AdvancePayment"]))
{
lv.SubItems.Add(System.Convert.ToString(Conversion.Val(total.ToString())));
}
else
{
lv.SubItems.Add("0");
}
lvlcheckin.Items.Add(lv);
}
rs.Dispose();
Module1.con.Close();

You are formatting the double using ToString("00.00") you cannot convert this string to an Int32...
Console.WriteLine(System.Convert.ToInt32("10.00")); // Will generate an error.
If you change your ToString("00.00") to ToString("00") it will work.
Although in general, I would prefer Int.TryParse so you can handle the error conditions. The following would return -1, if there is a parsing failuer (which there will be).
int cvt;
Console.WriteLine(Int32.TryParse("10.00", out cvt)?cvt:-1);

Yout problem is probably inside your if
if (Conversion.Val(subtotal.ToString()) > Conversion.Val(Dt.Rows[indx]["AdvancePayment"]))
The value of Dt.Rows[indx]["AdvancePayment"] is probably dynamic type, but as int not string. You used a ToString() method to calculate the same kind of value of the total variable. So, the sugestion is use ToString( inside the if too:
if (Conversion.Val(subtotal.ToString()) > Conversion.Val(Dt.Rows[indx]["AdvancePayment"].ToString()))
Please, next time tell us the line that the error throwed, or a better code (it depends your programming expecience)

Input string was not in a correct format. Expected type in Decimal type

I am not inserting any value in VOUCHER_NO column and updating it.
But it is giving me error as
Input string was not in a correct format.Couldn't store <> in VOUCHER_NO Column. Expected type is Decimal.
Below is my code
drpayinfo[0]["VOUCHER_NO"] = e.Record["VOUCHER_NO"];
Update
I am using Oracle DB and its datatype is NUMBER (10)

Seems your e.Record["VOUCHER_NO"] have some unwanted content which is not convertible to decimal. Try this way checking before assignment or conversion
if(e.Record["VOUCHER_NO"] != "")
{
drpayinfo[0]["VOUCHER_NO"] = Convert.ToDecimal(e.Record["VOUCHER_NO"]);
}
But more safer way to detect and ignore bad content is
decimal result;
if (Decimal.TryParse(e.Record["VOUCHER_NO"], out result))
{
drpayinfo[0]["VOUCHER_NO"] = result;
}
else
{
// do stuff if failed to parese
}

Based on your comments on other answers, your value is an empty string. This cannot directly be converted to a decimal. You must decide some action to take instead.
They following code will try to convert it, and take an action if not. TryParse is your friend for conversions!
decimal num = 0;
if (!Decimal.TryParse(e.Record["VOUCHER_NO"], out num))
{
//Throw some error, maybe set num to some default and assign...
//The appropriate action in this situation depends on your needs.
}
else
{
//You can safely assign the value
drpayinfo[0]["VOUCHER_NO"] = num;
}

Convert.ToInt32 user input array to int c#

I have the attached code which trys to find all 1s in an array input by the user.
The program asks the user to select the array size, then input a number of that size with some 1s in it. It then counts the number of 1s found.
I guess that the input the user gives is in the form of a string? So, if they input 12345 it would be a string with one 1 in it.
I am trying to convert the array to int32, though I don't think I fully understand why it has to be int32 either.
If somebody could help me understand this programs' workings and why I'm getting the following error I'd be thankful.
An unhandled exception of type 'System.FormatException' occurred in
mscorlib.dll Additional information: Input string was not in a correct
format.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace count1s
{
class Program
{
static void Main(string[] args)
{
int count = 0;
Console.WriteLine("Enter a number for the array length");
int limit = int.Parse(Console.ReadLine());
int[] array1s = new int[limit];
Console.WriteLine("Enter a number with some 1s in it");
for(int i=0; i<limit; i++)
{
array1s[i] = Convert.ToInt32(Console.ReadLine());
}
foreach (int number in array1s)
{
if (number == 1)
{
count++;
}
}
Console.WriteLine("The number of 1s in the array is: {0}", count);
Console.ReadLine();
}
}
}

You are getting this error because you are entering the array elements in one line.
If you enter one element on one line then program will work fine.
If you want to accept numbers on one line then you can use split function like
String []numbers = Console.ReadLine().Split(' ');
for (int i = 0; i < limit; i++)
{
array1s[i] = Convert.ToInt32(numbers[i]);
}
foreach (int number in array1s)
{
if (number == 1)
{
count++;
}
}

I don't think I fully understand why it has to be int32 either.
It doesn't have to be. That depends on your input. If the user enters a number small enough, it can also fit into a short (which is 16 bits), and you can parse the string into that.
why I'm getting the following error
Because you're trying to parse a string which isn't parse-able to a valid int value. If you're not sure the input is valid, you can use a method such as int.TryParse, which returns a boolean indicating the success or failure of the parsing:
int i = 0;
while (i < limit)
{
string value = Console.ReadLine();
int parsedValue;
if (!int.TryParse(value, out parsedValue))
{
Console.WriteLine("You've entered an invalid number. Please try again");
continue;
}
array[i] = parsedValue;
i++;
}
If you want to count all occurrences of 1, you can simply use Enumerable.Count which takes a predicate:
return array.Count(number => number == 1);

Use this as
for(int i=0; i<limit; i++)
{
int value;
var isNumber = int.TryParse(Console.ReadLine(), out value);
if(isNumber)
{
array1s[i] = value;
}
else
{
Console.WriteLine("Invalid value you have entered");
continue;
}
}

Well, now I feel like a bit of an idiot.
I tried some of your responses, thanks very much for that, and they are good. I went back and tried the code I originally posted as well and found that it does work. I just need to hit carriage return after each entry into the array.
I'll take a look at all of this properly later to find out what is going on.
Thanks again all - gotta say - was really surprised to get so many responses on here so quickly. Awesome!!

I just found a really good article on the Microsoft: DEV204x Programming with C# course I have started online. I think this will be helpful to all who follow with the same questions I had. Hopefully I'm not breaking any copyright laws or stackoverflow rules. It's a free course, so I doubt it.
Data Conversions
C# supports two inherent types of conversion (casting) for data types, implicit and explicit. C# will use implicit conversion where it can, mostly in the case when a conversion will not result in a loss of data or when the conversion is possible with a compatible data type. The following is an example of an implicit data conversion.
Converting from smaller to larger integral types:
int myInt = 2147483647;
long myLong= myInt;
The long type has a 64-bit size in memory while the int type uses 32-bits. Therefore, the long can easily accomodate any value stored in the int type. Going from a long to an int may result in data loss however and you should use explicit casting for that.
Explicit casts are accomplished in one of two ways as demonstrated with the following coe sample.
double myDouble = 1234.6;
int myInt;
// Cast double to int by placing the type modifier ahead of the type to be converted
// in parentheses
myInt = (int)myDouble;
The second option is to use the methods provided in the .NET Framework.
double myDouble = 1234.6;
int myInt;
// Cast double to int by using the Convert class and the ToInt32() method.
// This converts the double value to a 32-bit signed integer
myInt = Convert.ToInt32(myDouble);
You will find many other methods in the Convert class that cast to different integral data types such as ToBoolean(), ToByte(), ToChar(), etc.
The Convert.ToInt32() method can also be used to cast a string literal to a numeric data type. For example, you may have GUI-based application in which uses input data into text boxes. These values are string values when passed to the code in your application. Use of the above method to cast the string to numbers can help prevent exceptions in your code when trying to use the wrong data type in a specific area.
C# also provides another mechanism to deal with casting types. The use of the TryParse() method and Parse() methods can help with casting as well. These methods are attached to the types in C# rather than the Convert class. An example will help demonstrate.
// TryParse() example
bool result = Int32.TryParse(value, out number);
// Parse() example
int number = Int32.Parse(value);
In the TryParse() example, the method returns a Boolean result indicating if the conversion succeeded. In the Parse() example, if the conversion does not succeed, an exception will be thrown.

C# object and string conversion

I have following section of code in my program:
object val;
val = arr[1].Trim(); // in my case i am getting value here is 1.00
now when I am assigning value to a datarow I am getting error
Expected int64 value.
datarow[Convert.ToString(drow["col"]).Trim().ToUpper()] = val;
I am not facing any issue when getting value other that 1.00.
What could be the exact problem? How can I solve it?
Suggestions and solutions are welcome

If that column in your datatable is expecting an Int64 you need to convert val (which is a string) to an Int64:
var val = arr[1].Trim(); // String at this point
long longVal = 0;
if(!long.TryParse(val,out longVal){
throw new InvalidOperationException("value wasnt an Int64!");
}
datarow[Convert.ToString(drow["col"]).Trim().ToUpper()] = longVal

arr[1] seems to be string, and applying .Trim() keeps it as a string, even if it's "1.00". If you need an integer, you need to parse it. However, it can't be parsed to an intteger, because it's actually a double.
As a proof of whether I'm right or not, you can try (Int64)double.Parse(val) and that should work. However, it's up to you to decide whether that's not an issue for your program. There's two possible issues:
val might not be parse-able to double, in which case you will get an exception
val might be a double, but not one that can be represented as an int (too large, or lose precision ex. "1.8" would become 1)
Hope this helps

C# Input string was not in a correct format

Working on parsing from a text box to int to get into the incrementHour method as shown.
if (txtHourPlus.Text != String.Empty)
{
time1.incrementHour(int.Parse(txtHour.Text));
}
And in the time class: (the time1 objects class)
public int incrementHour(int step)
{
if (step > 0 && hour < 24)
{
//step = step % hour;
hour = (hour + step) % 24;
time.AddHours(hour);
return hour;
}//end of if
else
{
MessageBox.Show("Please enter a positive number.");
return 0;
}//end of else
}//end of incrementHour
not sure why i'm getting this error. I'm converting it to the corrent data type. Because it accepts an int variable.
Alright well i got it to take the value (small mistake >.> Don't even wanna say it)
However as someone already said the method probably needs work because i'm trying to change the Datetime value that i get in the first place and add an hour or subtract and etc etc.

That will happen if someone has typed "foo" into the text box, for example. You should use int.TryParse instead, which lets you detect the error without an exception being thrown.
I notice that you're not actually using the return value of your method though - just like you're not using the return value of time.AddHours. You are aware that DateTime.AddHours doesn't actually modify the value you're calling it on, aren't you? (I suspect you'll need to tweak that method quite a bit, actually... there are various potential problems with it, depending on exact what you're trying to do.)
(Finally, I'd change the method name to IncrementHour to comply with .NET conventions.)

you are testing txtHourPlus for emptiness, but then parsing and passing txtHour. typo (?)

If your input isn't parsable as an integer, attempting to parse it will raise an exception. Validate or use Int32.TryParse()

Change this part of your code:
if (txtHour.Text != String.Empty)
{
int parsedValue;
if (int.TryParse(txtHour.Text, out parsedValue))
{
time1.incrementHour(parsedValue);
}
else
{
// non-numeric value was entered into the textbox - handle accordingly.
}
}