I am in the process of converting some applications to C# by request of a client. I am new to C# so and have been stumped on some things. This is VS 3.5.

1)

I have a datarow that has a value in the ID column(Guid) and Title column (String). I am trying to set variables of the same type to the values of the datarow columns like so:

_id = dr["ID']

_title = dr["title"]

i am getting an error when building. Cannot implicitly convert type 'object' to 'Guid'. An explicit conversion exists (are you missing a cast?). Since the type is a uniqueidentifier (guid) from the query would that error converting guid to guid? There are times that the result set returns NULL so i don;t want to cast it. That would cause an error.

2)

In vb.net you can call a function and pass params in like so:

dothis( _

a, _

b, _

c)

in c# it won;t let you. You have to place them in a long string. I find that breaking the params into seperate lines is easier to read when you have some methods that have 20 or 30 params. is there an equivalent to this in c#?

3)

Is there an equivalent to the WithStatement in c#?

thanks all

j

Hi,

Try this
1.
if (dr["ID"] != null)
        {
            _id = dr["ID"].ToString();
        }
        if (dr["title"] != null)
        {
             _title = dr["title"].ToString();
        }

2.replace the _ by +

dothis(+
            +"a", +
            +"b", +
            +"c");

3.
try use using statement

1) use Convert.IsDBNull to check for DBNull

_id = Convert.IsDBNull(dr["ID"]) ? string.Empty : Convert.ToString(dr["ID"]);

_title = Convert.IsDBNull(dr["title']) ? string.Empty : Convert.ToString(dr["title']);

2) use without _

dothis(
a,
b,
c)

3) please refer to http://msdn.microsoft.com/en-us/vcsharp/aa336816.aspx

VB
With Button1
  .Text = "Hello"
  .BackColor = Color.Blue
End With

c#
Button1.Text = "Hello"
Button1.BackColor = Color.Blue

How would this work for a guid? Convert.IsDBNull(dr["ID"]) ? string.Empty : Convert.ToString(dr["ID"]);

------

i got it

thanks again

j

 2 more questions on this.

How do you handle DateTimes with this. You don't want to set a member of type DateTime to a value that is not a datetime. A string can be string.Empty. Do i just set the DateTime to Nothing or is there something else i shoudl do?

j

1)

C# requires that you explicitly convert types for everything but converions to base classes.  The error you're getting is the compiler telling you that you've violated this rule.  

If the DataSet can return null, what should the value of your _id field be when it does? (as an asside why are you ever having an ID that is nullable?)  If you need to store a null in there, I suggest declaring it as a Nullable<Guid> rather than just a Guid.  In this case you can reference System.Data.DatasetExtensions in your project and use the following:

_id = dr.Field<Nullable<Guid>>("ID");
_title = dr.Field<string>("title");
 

2)
do as such
    dothis(
        a,
        b,
        c);
Since linefeeds arent statement terminators in C#, you dont need any special syntax for continuing a statement on the next line.  the compiler sees a linefeed just like it sees a space.

3) No, but many of the uses of with statements can be simulated using the object initializer syntax