Create Tuple Using List of datatype of string in c#

user_5186174 0
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I need to create Tuple from list of datatype in string, but did not get any solution.

Here is example of what I want to do.

string[] dataType = {"int", "float", "datetime"};

//I want to create list like this but dynamically datatype come from db.
//List<Tuple<int, string, string>> list = new List<Tuple<int, string, string>>(); 

List<Tuple<dataType[0],dataType[1], dataType[2]>> list = new List<Tuple<dataType[0],dataType[1], dataType[2]>>();
//Here datatype value is in string so I want to convert string to actual datatype.

Or if any alternative solution for this please guide me.

tuples list c#
2 Answers

This is to extend my comments under question, and show you what I meant there.

It is not hard to create a list of Tuple dynamically from list of types in string format. For example, use reflection:

private Type InferType(string typeName)
{
    switch (typeName.ToLowerInvariant())
    {
        case "int":
            return typeof(int);
        case "float":
            return typeof(float);
        default:
            return Type.GetType($"System.{typeName}", true, true);
    }
}

private object CreateListOfTupleFromTypes(string[] types)
{
    var elementTypes = types.Select(InferType).ToArray();

    // Get Tuple<,,>
    var tupleDef = typeof(Tuple)
        .GetMethods(BindingFlags.Static | BindingFlags.Public)
        .First(mi => mi.Name == "Create"
            && mi.GetParameters().Count() == elementTypes.Length)
        .ReturnType
        .GetGenericTypeDefinition();

    // Get Tuple<int, float, DateTime>
    var tupleType = tupleDef.MakeGenericType(elementTypes);

    // Get List<Tuple<int, float, DateTime>>
    var listType = typeof(List<>).MakeGenericType(tupleType);

    // Create list of tuple.
    var list = Activator.CreateInstance(listType);

    return list;
}

The problem is because the list is created using types only known at runtime, in your code, you can never use the list as strong typed list. i.e.List<Tuple<int, float, DateTime>>.

Of course, you could make life easier when the list is used in your code by using ITuple:

var list = new List<ITuple>();
list.Add(new Tuple<int, float, DateTime>(...);

int value1 = (int)list[0][0];
float value1 = (float)list[0][1];
DateTime value1 = (DateTime)list[0][2];

However, if you do that, then there is no point to use Tuple. You only need List<object[]>.

So, this comes back to my question, what is the list of tuple for in your code?

user_106203170

You could use dynamic here for your types. For example, when you read the three values from your database you could assign them without worrying about the types like so:

dynamic a = 10;
dynamic b = "Some String";
dynamic c = new DateTime(2020,4,9);

var test = new System.Tuple<dynamic,dynamic,dynamic>(a, b, c);

It would depend on what you want to do with the values later on.

To create a list of those tuples use:

var list = new List<System.Tuple<dynamic,dynamic,dynamic>>();

You can get the type of the variable, for instance a with 

a.GetType().ToString();

I am not sure if you can set a variable type based on a string value, though (the second part of your question).

user_21466260
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