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specified cast is invalid

109 New Member
Hi

I am new to programming. learning c# , asp.net.

write a simple program: to get the id from database and save it to arraylist to find the max(id).

and getting exception: Specified cast is invalid.

at line: int low = (int)arrm[i];

Appreciate any help.

Thanks
Sep 12 '07 #1
27 2930
Shashi Sadasivan
1,435 Recognized Expert Top Contributor
Hi

I am new to programming. learning c# , asp.net.

write a simple program: to get the id from database and save it to arraylist to find the max(id).

and getting exception: Specified cast is invalid.

at line: int low = (int)arrm[i];

Appreciate any help.

Thanks
is arrm your table or the row?
if it is the table then arrm[i] is a row,
maybe what you want is
Expand|Select|Wrap|Line Numbers
  1. int i = (int)arrm[i][j];
Sep 12 '07 #2
arial
109 New Member
arram is a object of my array list.

Arraylist arrm = new Arraylist();

and here is part of my script:

cmd4.CommandTex t = "select id from dpt" ;
cmd4.ExecuteNon Query();
SqlDataReader reader = cmd4.ExecuteRea der();
while(reader.Re ad())
{
values = new object[reader.FieldCou nt];
reader.GetValue s(values);
arrm.Add(values );
}
arrm.Sort();
reader.Close();
cmd4.Connection .Close();

int max = 0;
for (int i = 0; i < arrm.Count; i++)
{
int min = (int)arrm[i];
if (max < min)
max = min;
}

}

Thanks,
Sep 13 '07 #3
Plater
7,872 Recognized Expert Expert
You could use the .GetType().Name on the arrm[i] to see what type the value is actually being returned as.

I would guess that if ID is defined as say "bigint" in the database, you would need to cast it to "Int64" and not just "int"
Sep 13 '07 #4
r035198x
13,262 MVP
arram is a object of my array list.

Arraylist arrm = new Arraylist();

and here is part of my script:

cmd4.CommandTex t = "select id from dpt" ;
cmd4.ExecuteNon Query();
SqlDataReader reader = cmd4.ExecuteRea der();
while(reader.Re ad())
{
values = new object[reader.FieldCou nt];
reader.GetValue s(values);
arrm.Add(values );
}
arrm.Sort();
reader.Close();
cmd4.Connection .Close();

int max = 0;
for (int i = 0; i < arrm.Count; i++)
{
int min = (int)arrm[i];
if (max < min)
max = min;
}

}

Thanks,
1.) Please use code tags when posting code.
2.) You have
Expand|Select|Wrap|Line Numbers
  1. arrm.Add(values);
which adds an array of objects into an arraylist. Then you have
Expand|Select|Wrap|Line Numbers
  1.              int min = (int)arrm[i];
which won't work because you're now trying to cast an object array to an int.
Sep 13 '07 #5
arial
109 New Member
ID is varchar field in sql database.

and .Getvalue().Nam e returns arraylist.

What I want to do is, find a max ID from table. I also tried Convert.ToInt32 (arrm[i]), but still no luck on getting what I want.

Thanks,
Sep 13 '07 #6
Plater
7,872 Recognized Expert Expert
There are SQL statements that will return to you the largest one. Google some SQL examples about it.

What r0 said was right (I missed it, good catch on his part) you are trying to cast an array of objects to an intiger.

And it's GetType().Name, which is available for everything and will identify what the object type is.
You don't need it now that it's been identified as an object[].
Sep 13 '07 #7
arial
109 New Member
Yes, I know sql statement will give me largest value but I need to use simple
select id from dpt and store this query result into array and find a max because I am going to use this array to do some other stuff.

If I can successfully get my first part right get max value and then it would be easy do the other parts.

so, is there a way to convert object type to int?

Thanks
Sep 13 '07 #8
Plater
7,872 Recognized Expert Expert
Since you are only returning a single value, using getValues() is a waste.

Expand|Select|Wrap|Line Numbers
  1. cmd4.CommandText = "select id from dpt" ; 
  2. cmd4.ExecuteNonQuery();
  3. SqlDataReader reader = cmd4.ExecuteReader();
  4. while(reader.Read())
  5. {
  6. int temp=reader.GetInt32(1);
  7. arrm.Add(temp);
  8. }
  9. arrm.Sort();
  10. reader.Close();
  11. cmd4.Connection.Close();
  12.  
  13. int max = 0;
  14. for (int i = 0; i < arrm.Count; i++)
  15. {
  16. int min = (int)arrm[i];
  17. if (max < min)
  18. max = min;
  19. }
  20.  
  21. }
  22.  
This might not be exactly right as I can't currently check it in a project, but hopefully it will make more sense as now your (int)arrm[i] shouldn't throw an exception.
Sep 14 '07 #9
arial
109 New Member
Thanks Plater for all your help.

By after making a changes you suggested Now I am getting new error:

Index was outside the bounds of the array.

at line: int temp=reader.Get Int32(1);
Sep 14 '07 #10

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