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POChecking if some function parameters data types are equal due compilation on C#
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2333039
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2010-02-25T09:48:29.390
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2010-02-25T13:06:43.467
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2010-02-25T13:06:43.467
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I have some example data: <pre><code>public struct Task { public int INT; public string STRING; public DateTime? NULLABLEDATETIME; } </code></pre> And function, which uses it: <pre><code>public KeyValuePair<Expression<Func<Task, object>>, object> Marry(Expression<Func<Task, object>> key, object value) { return new KeyValuePair<Expression<Func<Task, object>>, object>(key, value); } </code></pre> Here is example of function call: <pre><code>Marry(t => t.INT, 1984); Marry(t => t.NULLABLEDATETIME, DateTime.Now); Marry(t => t.STRING, "SomeSting"); </code></pre> This code works, no questions. Unfortunatly we can also call functions like below, because String and int are both inherited from object class: <pre><code>Marry(t => t.INT, "SomeSting"); </code></pre> I want to say compiler, that first and second parameters have same data type: <code>int -> int</code>, <code>string -> string</code>, <code>DateTime? -> DateTime?</code> and check it during compilation. I tried this: <pre><code>public KeyValuePair<Expression<Func<Task, T1>>, T2> Marry<T1, T2>(Expression<Func<Task, T1>> key, T2 value) where T2 : T1 { return new KeyValuePair<Expression<Func<Task, T1>>, T2>(key, value); } </code></pre> This almost works, and if I try to put wrong data like this <code>Marry(t => t.INT, "SomeSting");</code> the compiler reports an error: The type 'string' cannot be used as type parameter 'T2' in the generic type or method 'Task.Marry(System.Linq.Expressions.Expression>, T2)'. There is no implicit reference conversion from 'string' to 'int'. But this solution does not work with <code>null</code>. When I call <code>Marry(t => t.NULLABLEDATETIME, null);</code> the compiler says: The type arguments for method 'Marry(System.Linq.Expressions.Expression>, T2)' cannot be inferred from the usage. Try specifying the type arguments explicitly. Why? I already know the data type: <code>DateTime?</code>. I don't want to explicitly call <code>Marry<DateTime?>(t => t.NULLABLEDATETIME, null);</code>. How can I do this - or is there another way to check some function parameter types during compilation?
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<c#><generics><parameters><types><constraints>
Title
Checking if some function parameters data types are equal due compilation on C#
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1. USEamon Nerbonne
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1. USOleg Mazko
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