CODEWITHSUNDEEP
c#
Mike Baxter
Mike Baxter

Reputation: 7268

Specified cast is not valid: numeric cell to int?

Usually "specified cast is not valid" errors are easy to solve. But this one has gotten my head scratching.

I have a SQL compact database integrated in my C# application. At the moment I am getting the current database structure and putting it into a datatable. The SQL command im using is:

select * from information_schema.columns

One of the columns is NUMERIC_PRECISION, which is a numeric value.

I try and store this information in an integer variable, but it tells me the specified cast is not valid. The code is:

int precision;
if (row["NUMERIC_PRECISION"] != DBNull.Value)
    precision = (int)row["NUMERIC_PRECISION"];

My question is why is this operation invalid? The cell is a numeric value and I am trying to cast it to an integer - surely in theory this should work?

Upvotes: 0

Views: 2220

Answers (5)

Vishal Suthar
Vishal Suthar

Reputation: 17194

The best practice is to: int.Parse(string s)

precision= Convert.ToInt32(row["NUMERIC_PRECISION"]);

Upvotes: 0

Matthew Watson
Matthew Watson

Reputation: 109577

[EDIT] Now you said it's a string: You must parse it.

Try: precision = int.Parse((string)row["NUMERIC_PRECISION"]);

That will throw an exception if it isn't in the correct format, so you must either be prepared to catch the exception, or use an overload of int.TryParse() to check its validity.

[EDIT2]

It seems that the data is not a string; it is an Int16. So do this:

precision = (Int16)row["NUMERIC_PRECISION"];

Upvotes: 0

Nevyn
Nevyn

Reputation: 2683

since you said that the value could be null, I would actually use a nullable integer to store it in.

int? precision = null;

if(row["NUMERIC_PRECISION"] != DBNull.Value) //or whatever you want to do to make sure it actually has a value
{
    //I usually use Convert.ToInt32 since its easier, but it is also more sensative
    precision = Convert.ToInt32(row["NUMERIC_PRECISION"]);
}

the Convert class is easy to use and visibly makes a lot of sense, its very sensitive to null or improperly formatted values though, and throws an exception when it finds one.

Upvotes: 2

Dor Cohen
Dor Cohen

Reputation: 17080

Try using int.parse instead of simple casting to int - http://msdn.microsoft.com/en-us/library/system.int32.parse.aspx

Upvotes: 0

alex
alex

Reputation: 12654

row["NUMERIC_PRECISION"] returns object that has an numberic typed boxed in it. You can cast it only to the exact type of this boxed object.

try casting to (decimal) or (long) first , and then to (int).

You can check the type of row["NUMERIC_PRECISION"] using debugger watch.

You can also ask Convert class to handle conversion for you:

precision = Convert.ToInt32(row["NUMERIC_PRECISION"]);

Upvotes: 1

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