How to Handle Nullable Values in LINQ Queries Like SQL's ISNULL?

Nullable Values in LINQ Queries

In SQL, the ISNULL function allows for the substitution of an empty string for null values. When translating this functionality to LINQ queries, a similar approach can be adopted.

Consider this LINQ query that includes a join with a nullable bit column named xx.Online:

var hht = from x in db.HandheldAssets
        join a in db.HandheldDevInfos on x.AssetID equals a.DevName into DevInfo
        from aa in DevInfo.DefaultIfEmpty()
        select new
        {
        AssetID = x.AssetID,
        Status = xx.Online
        };

To account for potential null values in aa.Online, a null-conditional operator can be employed:

select new {
    AssetID = x.AssetID,
    Status = aa == null ? (bool?)null : aa.Online; // a Nullable<bool>
}

This check ensures that aa is not null before accessing its Online property. If aa is null, the result will be a null Boolean value.

Another option is to assign a default value (e.g., false) to null values:

select new {
    AssetID = x.AssetID,
    Status = aa == null ? false : aa.Online;
}

In this scenario, null values will be replaced with the specified default value.

By utilizing these techniques, it is possible to handle null values in LINQ queries similarly to how ISNULL is used in SQL.

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