coalescing operator work in this case?

2018-06-19 02:48:58

This question already has an answer here:

Unable to cast object of type 'System.DBNull' to type 'System.String` 10 answers

What do two question marks together mean in C#? 16 answers

DBNull isn't the same as null , so you can't use the ?? operator. You have to handle this case separately.

Replace:

Make = (string)(rdr["Make"] ?? ""),

with:

Make =  (rdr["Make"] == System.DBNull.Value ? "" : (string)rdr["Make"]),

SqlDataReader returns a DBNull object, which is not a C# null - it is an object representing a NULL value in the database.

You have a number of options, and creating a method to handle that might be most readable and save you on repeating code:

private static string GetStringOrEmpty(object dbValue){
    return dbValue == System.DBNull.Value ? string.Empty : (string)dbValue;
}

and then

Make = GetStringOrEmpty(rdr["Make"]),

Alternatively look into Dapper which is a very small but powerful ORM that will handle a lot of this stuff for you.

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