If/Else in Inline Synatx to declase class object with properties C#

Question

I have requirement to dynamically add property values based on column values. Current I am creating object as below:

while (rd.Read())
 {
   list.Add(new DeviceModelInfo()
    {
       ID = rd.GetGuid("ID"),
       Manufacturer = new Manufacturer()
       {
         ID = rd.GetGuid("ManufacturerID"),
         Name = rd.GetString("ManufacturerName"),
         ManufacturerType (ManufacturerEnum)rd.GetInt32("ManufecturerType")
       },
       Model = rd.GetString("Model"),
       IMEI = rd.GetString("IMEI")
    });
 }

But I need to check if IMEI column is available or not in DataReader but when I am using if else then its giving syntax error I want to add IMEI if its available in DataReader how can I achieve that?

 if (rd.GetName(i).Equals("IMEI", StringComparison.InvariantCultureIgnoreCase))
    IMEI = rd.GetString("IMEI")

Where does `i` suddenly come from? Do you have a method of checking, if a specific column name exists? Something like this https://stackoverflow.com/a/813741/1336590 — Corak, Apr 03 '18 at 05:28

Jon Skeet · Accepted Answer · 2018-04-03T06:01:46.197

I'm assuming i is already a variable somewhere which has the number of the column that will be the IMEI if it's available. If that's not the case, see the end of the answer.

You can't use an if statement in an object initializer. What you could do is separate it out into a separate statement:

while (rd.Read())
{
    var device = new DeviceModlInfo
    {
        ID = rd.GetGuid("ID"),
        Manufacturer = new Manufacturer()
        {
           ID = rd.GetGuid("ManufacturerID"),
           Name = rd.GetString("ManufacturerName"),
           ManufacturerType (ManufacturerEnum)rd.GetInt32("ManufecturerType")
        },
        Model = rd.GetString("Model");
    };
    if (rd.GetName(i).Equals("IMEI", StringComparison.InvariantCultureIgnoreCase))
    {
        device.IMEI = rd.GetString("IMEI");
    }
    list.Add(device);
}

Alternatively, you could use the conditional ?: operator to assign one value or another to IMEI based on a condition:

while (rd.Read())
{
    list.Add(new DeviceModelInfo
    {
       ID = rd.GetGuid("ID"),
       Manufacturer = new Manufacturer()
       {
           ID = rd.GetGuid("ManufacturerID"),
           Name = rd.GetString("ManufacturerName"),
           ManufacturerType (ManufacturerEnum)rd.GetInt32("ManufecturerType")
       },
       Model = rd.GetString("Model"),
       IMEI = rd.GetName(i).Equals("IMEI", StringComparison.InvariantCultureIgnoreCase))
            ? rd.GetString("IMEI") : null;
   });

}

If you actually don't know which column would be the IMEI, I'd probably write a separate method to check whether the column is present or not, just once. You'd then write (outside the loop):

int? imeiColumn = GetColumn(dr, "IMEI");

Then in your object initializer, write:

IMEI = imeiColumn != null ? dr.GetString(imeiColumn.Value) : null

Where GetColumn might look something like:

static int? GetColumn(DbDataReader reader, string name)
{
    for (int i = 0; i < reader.VisibleFieldCount; i++)
    {
        if (reader.GetName(i).Equals(name, StringComparison.InvariantCultureIgnoreCase))
        {
            return i;
        }
    }
    return null;
}

@GaurangDave: See my edit for both the case where it's known as the column that will contain the IMEI if it's present, or not (at the bottom). — Jon Skeet, Apr 03 '18 at 05:30

Gaurang Dave · Answer 2 · 2018-04-03T05:39:23.697

You can use this extension method:

public static bool ColumnExists(this IDataRecord dr, string ColumnName)
{
    for (int i=0; i < dr.FieldCount; i++)
    {
        if (dr.GetName(i).Equals(ColumnName, StringComparison.InvariantCultureIgnoreCase))
            return true;
    }
    return false;
}

Use:

while (rd.Read())
{
    if(rd.ColumnExists("IMEI"))
    // DO YOUR WORK
}

Another way using LINQ:

Only work with .NET 3.5 and above

 while (rd.Read())
 {
     if(Enumerable.Range(0, rd.FieldCount).Any(c => rd.GetName(c) == "IMEI"))
     // DO YOUR WORK
 }

Abhilash Ravindran C K · Answer 3 · 2018-04-03T05:50:15.313

0

You can use conditional operator ?: to check whether IMEI column exist or not. If Column exist then get the value otherwise set IMEI value as No IMEI( whatever you like)

So change,

IMEI = rd.GetString("IMEI") //Inside list.Add(new DeviceModelInfo()..)

to

IMEI = rd.GetName(i).Equals("IMEI", StringComparison.InvariantCultureIgnoreCase) ? rd.GetString("IMEI"):"No IMEI"

edited Apr 03 '18 at 05:50

answered Apr 03 '18 at 05:33

Abhilash Ravindran C K

1,818
2
13
22

Where the `i` comes from? – Chetan Apr 03 '18 at 05:33
May be from outer loop, that is up to him as he gave condition as like that in if statement. This code will be helpful to him. – Abhilash Ravindran C K Apr 03 '18 at 05:36

If/Else in Inline Synatx to declase class object with properties C#

3 Answers3