Question

I’m developing a WCF web services and I use ADO.Net Entities to access database.

I use this method to convert some Database objects to Contract objects:

public static List<BlockContract> FormBlocks(int formId)
{
    List<BlockContract> blocksList = null;

    using (var vAdmEntities = new ADMDatabase.ADMEntities())
    {
        var blockEntities = from f in vAdmEntities.Form
                        where f.formId == formId
                        select f.Block;
        if (blockEntities != null)
        {
            blocksList = new List<BlockContract>(blockEntities.Count());
            foreach (ADMDatabase.Block b in blockEntities)
            {
                BlockContract blockContract = new BlockContract
                {
                    blockId = b.blockId,
                    name = b.name,
                    orderInForm = b.orderInForm
                };
                blocksList.Add(blockContract);
            }
        }
    }

    return blocksList;
}

Here, foreach (ADMDatabase.Block b in blockEntities), I get an error:

Cannot convert type 'System.Data.Objects.DataClasses.EntityCollection<ADMDatabase.Block>' to 'ADMDatabase.Block'

How can I solve this error?

Answer 1

You need to change your loop;

foreach (var blockItems in blockEntities){
     foreach (ADMDatabase.Block b in blockItems)
            {
                BlockContract blockContract = new BlockContract
                {
                    blockId = b.blockId,
                    name = b.name,
                    orderInForm = b.orderInForm
                };
                blocksList.Add(blockContract);
            }
}

you are selecting blockentities with the following;

var blockEntities = from f in vAdmEntities.Form
                        where f.formId == formId
                        select f.Block;

Here if you debug blockEntities you will something like a list of lists since Form.Block is a list of block items.