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Expression.ArrayAccess () on IDictionary <string, object> by key name

How do I create an expression tree to read a value on an array access for IDictionary<string,object>

?

I want to present:

((IDictionary<string,object>)T)["KeyName"]

I cannot find an example of using ArrayAccess for string name access. I need something like:

var parameterExpression = Expression.Parameter(typeof(IDictionary<string, object>));

var paramIndex = Expression.Constant("KeyName");

var arrayAccess = Expression.ArrayAccess(parameterExpression, paramIndex);

I am getting the error this is not an array. What is the correct way to do this?

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1 answer


You might * want to access the property Item

:

var dic = new Dictionary<string, object> {
    {"KeyName", 1}
};
var parameterExpression = Expression.Parameter(typeof (IDictionary<string, object>), "d");
var constant = Expression.Constant("KeyName");
var propertyGetter = Expression.Property(parameterExpression, "Item", constant);

var expr = Expression.Lambda<Func<IDictionary<string, object>, object>>(propertyGetter, parameterExpression).Compile();

Console.WriteLine(expr(dic));

If you pulled the hood in the class using the indexer, there is a property Item

. Consider this example:



class HasIndexer {
    public object this[int index] {
        get { return null; }
    }
}

has the following (applies to indexers) IL:

.property instance object Item(
    int32 index
)
{
    .get instance object ConsoleApplication8.HasIndexer::get_Item(int32)
}

.method public hidebysig specialname 
    instance object get_Item (
        int32 index
    ) cil managed 
{
    // Method begins at RVA 0x2050
    // Code size 2 (0x2)
    .maxstack 8

    IL_0000: ldnull
    IL_0001: ret
} // end of method HasIndexer::get_Item
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