Casting vs Converting an object toString, when object really is a string

Question

This isn\'t really an issue, however I am curious. When I save a string in lets say an DataRow, it is cast to Object. When I want to use it, I have to cast it ToString. As f

Answer 1

I want to make one more comment

If you are going to use casting: string name = (string)DataRowObject["name"] you will get an Exception: Unable to cast object of type 'System.DBNull' to type'System.String' in case if the record in the database table has null value.

In this scenario you have to use: string name = DataRowObject["name"].ToString() or

You have to check for null value like

if(!string.IsNullOrEmpty(DataRowObject["name"].ToString()))
{
string name = (string)DataRowObject["name"];
}
else
{
//i.e Write error to the log file
string error = "The database table has a null value";

}

Answer 2

Downcasting is a relatively slow operation since CLR has to perform various runtime type-checks. However, in this particular scenario casting to string is more appropriate than calling ToString() for the sake of consistency (you can't call ToInt32 on object, but cast it to int) and maintanability.

Answer 3

I know you mentioned that the Object is a string, but incase you're afraid that the returned object is null, you can also cast using "Convert.ToString(DataRowObject["name"]);" This has the added benefit of returning an empty string (string.empty) if the object is null, to avoid any null reference exceptions (unless of course you want an exception thrown in such cases).

Answer 4

For data object, I suggest you to use "as" keyword like the following code.

string name = DataRowObject["name"] as string;

Please check it before you use value.

if(name != null)
{
    // statement for empty string or it has value
}
else
{
    // statement for no data in this object.    
}

Answer 5

Basically in your case it is better to leave type cast because .ToString() may hide bugs. For example, your data base schema changed and name is no longer of string type but with .ToString() your code still works. So in this case it is better to use type cast.

Here is implementation of String.ToString() - nothing special =)

public override string ToString()
{
    return this;
}

Answer 6

ToString() does not perform a cast by default. Its purpose is to return a string that represents the type (e.g. "System.Object").

If you want to avoid casting you could try to think of an implementation that is strongly typed (using generics, for example) and avoids DataRowObject altogether.