Compare and Null

  • Thread starter Thread starter shapper
  • Start date Start date
S

shapper

Hello,

I created a method to check if two objects (string, int, ...) are
equal.

The objects should only be compared if they are not null or in case of
a string also empty.

I am using the following:

// Equal
public static bool Equal(object value, object compare) {

CaseInsensitiveComparer comparer =
CaseInsensitiveComparer.DefaultInvariant;

if (value == null ? true : (String.IsNullOrEmpty(value.ToString
()) ? true : false)) return true;

if (compare == null ? true : (String.IsNullOrEmpty
(compare.ToString()) ? true : false)) return true;

return comparer.Compare(value, compare) == 0;

} // Equal

This is working but am I checking all the cases where the Compare
would throw an error?

Thanks,
Miguel
 
shapper said:
Hello,

I created a method to check if two objects (string, int, ...) are
equal.

The objects should only be compared if they are not null or in case of
a string also empty.

I am using the following:

// Equal
public static bool Equal(object value, object compare) {

CaseInsensitiveComparer comparer =
CaseInsensitiveComparer.DefaultInvariant;

if (value == null ? true : (String.IsNullOrEmpty(value.ToString
()) ? true : false)) return true;

if (compare == null ? true : (String.IsNullOrEmpty
(compare.ToString()) ? true : false)) return true;
Click to expand...

That's one of the most convoluted ways of writing a conditions I have
seen...

if (value == null || string.IsNullOrEmpty(value.ToString())) return true;
if (compare == null || string.IsNullOrEmpty(compare.ToString())) return
true;

But are you sure that those should return true? That means that
Equal("Hello", "") and Equal(DbNull.Value, "anything") return true...
return comparer.Compare(value, compare) == 0;
Click to expand...

That only works if one of the objects implements the IComparable interface.
 
shapper said:
Hello,

I created a method to check if two objects (string, int, ...) are
equal.

The objects should only be compared if they are not null or in case of
a string also empty.

I am using the following:

// Equal
public static bool Equal(object value, object compare) {

CaseInsensitiveComparer comparer =
CaseInsensitiveComparer.DefaultInvariant;

if (value == null ? true : (String.IsNullOrEmpty(value.ToString
()) ? true : false)) return true;

if (compare == null ? true : (String.IsNullOrEmpty
(compare.ToString()) ? true : false)) return true;

return comparer.Compare(value, compare) == 0;

} // Equal

This is working but am I checking all the cases where the Compare
would throw an error?

Thanks,
Miguel
Click to expand...

Hi Miguel,

If null is not allowed this comparing algorithm should be sufficient

public static bool Equal(object value, object target)
{
if (value == null || target == null)
return false;

CaseInsensitiveComparer comparer =
CaseInsensitiveComparer.DefaultInvariant;
return comparer.Compare(value, target) == 0;
}

It would consider two empty strings to be equal, but if that is not
desirable add

if(value.ToString() == String.Empty || target.ToString() == String.Empty)
return false;

If you also won't compare two different types add a

if(value.GetType() != target.GetType())
return false;
 
shapper said:
Hello,

I created a method to check if two objects (string, int, ...) are
equal.

The objects should only be compared if they are not null or in case of
a string also empty.

I am using the following:

// Equal
public static bool Equal(object value, object compare) {

CaseInsensitiveComparer comparer =
CaseInsensitiveComparer.DefaultInvariant;

if (value == null ? true : (String.IsNullOrEmpty(value.ToString
()) ? true : false)) return true;

if (compare == null ? true : (String.IsNullOrEmpty
(compare.ToString()) ? true : false)) return true;

return comparer.Compare(value, compare) == 0;

} // Equal

This is working but am I checking all the cases where the Compare
would throw an error?

Thanks,
Miguel
Click to expand...

Actually, in addition to my other posts, comparers often require the target
type to be the same type as the value so. To sum it up:

public static bool Equal(object value, object target)
{
if (value == null || target == null)
return false;

if (value.GetType() != target.GetType())
return false;

if (!(value is IComparable))
return false;

CaseInsensitiveComparer comparer =
CaseInsensitiveComparer.DefaultInvariant;
return comparer.Compare(value, target) == 0;
}
 
Morten said:
Hi Miguel,

If null is not allowed this comparing algorithm should be sufficient

public static bool Equal(object value, object target)
{
if (value == null || target == null)
return false;

CaseInsensitiveComparer comparer =
CaseInsensitiveComparer.DefaultInvariant;
return comparer.Compare(value, target) == 0;
}
Click to expand...

That still throws an exception if none of the obejcts implement the
IComparable interface.
 
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