Entity Framework/Linq Expression Converting from String to Int

Entity Framework/Linq EXpression converting from string to int

As pointed out by others in the comments, the fact that you're having to parse this value should be a red flag that you should be using a different data type in your database.

Fortunately, there is a workaround by forcing the query to be executed by LINQ to Objects rather than LINQ to Entities. Unfortunately, it means potentially reading a large amount of data into memory

EDIT

Based on your other comments, the value in the Value column ins't guaranteed to be a number. Therefore, you'll have to try converting the value to a number and then handling things based on the failure/success of that conversion:

return message
       .Properties
       .AsEnumerable()
       .Any(p => 
            {
                var val = 0;
                if(int.TryParse(p.Value, out val))
                {
                    return p.Key == name &&
                           val >= values[0] &&
                           val <= values[1])
                }
                else
                {
                    return false;
                }
           );

EDIT 2

You might actually be able to get away with this in the database. I'm not sure if this will work or not for you but give it a shot:

return message.Properties
              .Where(p => p.Key == name && SqlFunctions.IsNumeric(p.Value) > 0)
              .Any(p => Convert.ToInt32(p.Value) >= values[0] &&
                        Convert.ToInt32(p.Value) <= values[1]);

How to convert string to int in linq to entity?

Here you say:

tr.ProductID is a int

And then you try:

convert.toint32(tr.ProductID)

So... you're trying to convert an int to an int? In a comment you say:

the best overload method match for int.parse(string) has some invalid arguments

Well, if you're trying to call int.Parse() and passing it an int then you'd probably get that exact error. I imagine there's no overload for int.Parse() which accepts an int since, well, the value is already an int.

Let's look back at your problem description:

tr.ProductID is a int and wr.PKfWarranty is String

And you want to compare these two values? Then you'll either need to convert tr.ProductID to a string:

tr.ProductID.ToString()

or convert wr.PKfWarranty to an int:

int.Parse(wr.PKfWarranty)

A few things to note:

Converting from an int to a string is pretty safe, I doubt you'll ever have problems with that. However, converting from a string to an int assumes that the string can be converted to an int. This won't be the case if the string has anything in it that's not an int, or has a number too large to fit into the int data type. int.TryParse() exists for this purpose, but can be tricky to use in an in-line LINQ statement, especially when that statement is an expression tree which needs to produce SQL code.
If you convert the int to a string, there are different ways to compare strings. Depending on whether this is happening in resulting SQL code or in C# code makes a difference. If the latter, string.Equals() is the preferred method.

Convert 'string' to 'int' in an .Any() LINQ query

According to your code you when m.Reference is not a valid number the condition should fail, this can be done using SqlFunctions.IsNumeric().

To compare numbers you can use string.Compare and simulate numeric comparison padding left with 0s (it's possible with SqlFunctions.Replicate()).

It's not too pretty, but should works:

var itemId = item.ShoppingCartWebId.ToString();

ctx.CustomerInboxes.Any(m => ...
                          && SqlFunctions.IsNumeric(m.Reference) != 0 
                          && string.Compare(SqlFunctions.Replicate("0", m.Reference.Length > itemId.Length ? m.Reference.Length - itemId.Length : 0) + itemId, m.Reference) > 0);

However you always can switch to Linq to Objects to check this specific part:

ctx.CustomerInboxes.Where(m => m.CustomerId == customerId &&
                               m.Reference == item.ShoppingCartWebId.ToString()  &&
                               m.SubjectId == HerdbookConstants.PendingCartMessage)
                    .AsEnumerable()
                    .Any(c => item.ShoppingCartWebId > (long.TryParse(c.Reference, out t) ? t : long.MaxValue))

Convert string to int in an Entity Framework linq query and handling the parsing exception

First way:

var numbers = Purchases.Select(x => x.Number).ToList();

int temp;
int max = numbers.Select(n => int.TryParse(n, out temp) ? temp : 0).Max();

Console.WriteLine("Max: {0}", max);

Second way:

int temp2;
int max2 = Purchases.Select(x => x.Number).ToList().Select(n => int.TryParse(n, out temp2) ? temp2 : 0).Max();

Console.WriteLine("Max 2: {0}", max2);

The key is the .ToList() in those two ways. It gets all the string data from the database, so when you call int.TryParse on the results, the database query has already been run, so it is using pure CLR code, and not trying to convert int.TryParse into a SQL query. I made an EF context in one of my Sandbox projects and verified this works.

Converting string to int in linq to entities on big database

I think it is quite safe to do the comparison as string, unless you have years < 1000 or > 9999:

... dr.stringYear.CompareTo(myNumberString) > 0

EF translates this into a SQL predicate like

WHERE [alias].[stringYear] > @p

which is possible in SQL but not in C#.

An advantage would be that any index on stringYear may be usable in an execution plan. Converting stringYear to number eliminates any index.

This method is still useful when the string column contains jagged string values. In such a case the predicate should be combined with Length. For example, to find all entities where any numeric string as integer is greater than some reference value

var len = myNumberString.Lenght;

var query = 
    from row in context.LegacyTable
    where row.NumericString.CompareTo(myNumberString) > 0
       && row.NumericString.Length >= len
    select row;

Then the query engine can't use indexes for the length comparison but it might be able to do so for the > comparison.

LINQ converting string to int

Try moving the conversion outside of the query.

var dataSet = entities.BL_FERRERO_MT_CATEGORY
        .Distinct()
        .Where(d => (iGeography.FirstOrDefault() == "" || iGeography.Contains(d.Geography))
        && (iRetailer.FirstOrDefault() == "" || iRetailer.Contains(d.Retailer))
        && (iCountry.FirstOrDefault() == "" || iCountry.Contains(d.Country))
        && (iAirport.FirstOrDefault() == "" || iAirport.Contains(d.Airport))
        && (iShop.FirstOrDefault() == "" || iShop.Contains(d.StoreName))
        && (iCategory.Contains(d.Category))
        && (d.Values == "Sum of EuroValue"))
        .ToList()
        .GroupBy(x => x.Category)
        .Select(g => new {
            C201408 = g.Sum(x => Convert.ToInt32(x.C201408))});

This is make the LINQ to Entities convert the valid query. After that it will perform the grouping and selection of the .Sum().

Linq to entities Expression parse string to int

Finaly I found the solution it was just a matter of operator:

The goal of the expression was to obtain a linq query like this:

bookProperty.Where(b=> b.type== "taille && b.value == 1)

For that I used Expression.And() operator.
That was the mistake: && correspond ton AndAlso operator

Convert string to int in LINQ to Entities?

Do the conversion outside LINQ:

var idInt = Convert.ToInt32(id);
var query = (from p in dc.CustomerBranch
             where p.ID == idInt 
             select new Location()
             {
                 Name      = p.BranchName,
                 Address   = p.Address,
                 Postcode  = p.Postcode,
                 City      = p.City,
                 Telephone = p.Telephone
             }).First();
return query;

Entity Framework/Linq Expression Converting from String to Int