Vfrdtyky

Someone has posted a similar question here How Dynamic library (System.Linq.Dynamic) support LIKE Operator?

But it's not exactly what I want. The Contains operator mentioned in that post only do this in SQL "%SOMETHING%". But the LIKE operator in SQL can do this "SOME%THING". Is there a similar operator for Dynamic LINQ? If not, is there a solution for this? Maybe with Regex? Also is there a single character wildcard? E.g. "SOM$THING" returns "SOMETHING" or "SOM3THING"

Edit: I am developing a WPF application which should read log files in XML format. Each element contains 34 fields. So instead of writing a very long WHERE, I have used System.Reflection.PropertyInfo to iterate each field to write the query and then use System.Linq.Dynamic to execute it.

Edit2: I have edited the code so it's more readable for the viewers.

Here is some code:

Example 1:
prop.Name = "FirstName", paramterString = "Ke%in", returns "Kevin",
"Kelvin"...
Example 2:
prop.Name = "FirstName", paramterString = "Ke$in", returns "Kevin",
"Kelin"...

var query = "";

StringBuilder sb = new StringBuilder();

foreach (var prop in stringProps)

{

    sb.Append($"({prop.Name} != null And {prop.Name}.Contains({parameterString})");

}

query = sb.ToString().Substring(0, sb.Length - 4);

filteredData = filteredData.Where(query);

One of the requirement is to implement a SQL LIKE operator, so the users can use something like this to get the result they want: FirstName LIKE 'SOME%THING'

Since there is no LIKE operator in Dynamic Linq library, I have created it my own version. The code is not pretty, but it does work. Hopefully someone can optimize it or suggest a better way to do this.

public string ParseWildcardInParameterString(string parameter, string propertyName)

{

    string stringWithWildcard = parameter;

    if (parameter.Contains("%") || parameter.Contains("$"))

    {

        stringWithWildcard = parameter;

        string substrings = parameter.Split(new Char { '%', '$' }, StringSplitOptions.RemoveEmptyEntries);

        string wildcards = ParseWildcards(parameter);

        if (substrings.Any())

        {

            StringBuilder sb = new StringBuilder();

            int substringsCount = substrings.Length;

            for (int i = 0; i < substringsCount; i++)

            {

                if (!substrings[i].EndsWith("\"))

                {

                    int index = parameter.IndexOf(substrings[i]);

                    if (i < substringsCount - 1)

                    {

                        index = parameter.IndexOf(substrings[i + 1], index + 1);

                        if (index > -1)

                        {

                            string secondPart = wildcards[i].Equals("%") ?

                                $"{propertyName}.IndexOf("{substrings[i + 1]}", {propertyName}.IndexOf("{substrings[i]}") + "{substrings[i]}".Length) > -1" :

                                $"{propertyName}.IndexOf("{substrings[i + 1]}", {propertyName}.IndexOf("{substrings[i]}") + "{substrings[i]}".Length + 1) == {propertyName}.IndexOf("{substrings[i]}") + "{substrings[i]}".Length + 1";

                            sb.Append($"({propertyName}.IndexOf("{substrings[i]}") > -1 And {secondPart}) And ");

                        }

                    }

                }

            }

            stringWithWildcard = sb.Remove(sb.Length - 5, 5).Append(") Or ").ToString();

        }

    }

    return stringWithWildcard;

}



private string ParseWildcards(string parameter)

{

    IList<string> wildcards = new List<string>();

    foreach (var chararcter in parameter.ToCharArray())

    {

        if (chararcter.Equals('%') || chararcter.Equals('$'))

        {

            wildcards.Add(chararcter.ToString());

        }

    }

    return wildcards.ToArray();

}

Can you try if the Like functionality in System.Linq.Dynamic.Core does work for you?

Code example would be:

var dynamicFunctionsLike1 = context.Cars.Where(config, "DynamicFunctions.Like(Brand, "%a%")");

For full example, see ConsoleAppEF2.1.1/Program.cs