CODEWITHSUNDEEP
.netguid
Dooie
Dooie

Reputation: 1669

cannot convert from 'System.Guid?' to 'System.Guid'

Does anyone know how to deal with this error?

cannot convert from 'System.Guid?' to 'System.Guid'

Upvotes: 28

Views: 58496

Answers (6)

sametcekin
sametcekin

Reputation: 91

If you are sure value is not null then you can cast value as a (Guid)

var identifier = (Guid)myOtherIdentifier!;

Or you can use

var identifier = myOtherIdentifier.HasValue ? myOtherIdentifier : Guid.Empty;

Or another usage is

var identifier = myOtherIdentifier ?? Guid.Empty;

Upvotes: 0

Niraj Trivedi
Niraj Trivedi

Reputation: 2860

Use Guid?.Value property to convert 'System.Guid?' to 'System.Guid'. as following example

Obj GetValue(Guid yourID)
{
return FetchObject(yourID)
}
Void main()
{
Guid? passvalue;
Obj test = GetValue(passvalue.Value);
}

Upvotes: 6

Anirudh Singh Rawat
Anirudh Singh Rawat

Reputation: 229

Simply use Nullable<T>.HasValue in if statement to check the value for null, then after it you can use Nullable<T>.Value to gets the value of an underlying type.

int? a = null;
if(a.HasValue){
  Console.WriteLine($"a has value {a.Value}");
} else {
  Console.WriteLine("No value found in a");
}

Upvotes: 2

Nigel Givans
Nigel Givans

Reputation: 464

cannot convert from 'System.Guid?' to 'System.Guid'

you are trying to save type System.Guid? to a type system.Guid inside your model you can edit System.Guid? to System.Guid by removing the question mark.

or RCIX answer above

Upvotes: 0

Sandy
Sandy

Reputation: 817

First intialize the guid variable.

Guid yourGuid= Guid.NewGuid()

then set value in that which you want for eg:

 Guid defaultId = Guid.NewGuid();
 if (customerRow.GuardianState.Length > 2) {
 Guid StateId = record.StateId ?? defaultId;}

Upvotes: 1

RCIX
RCIX

Reputation: 39427

See MSDN.

In that case, merely use myNullableVariable.Value (if you're sure it has a value), or (myNullableVariable.HasValue)?myNullableVariable.Value:somedefaulthere if you're not.

One can also use GetValueOrDefault() if one doesn't care if the default is a specific value when the nullable really is null.

The last way to do it is this: myNullableVariable.Value ?? defaultvalue.

See, technically a MyType? variable is a Nullable<MyType> under the covers. There are no implicit or explicit casts between the two, so what you need to do is extract the value out of the Nullable manually. The third way i listed is the most succinct (and best?) way to do it, to that would probably be best in most cases.

Upvotes: 61

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