Question 213409 in ASP.NET Question posted in
The official documentation can be found here.

Asp.net – Questions about Expression<Func<ExpandoObject, object>> in C#

known conditions:

public class ListSearchImportFieldModel
{
    public string Field_Name { get; set; }
}

I need to implement the following method
Return properties of ListSearchImportFieldModel as properties of ExpandoObject function as follows:

enter image description here

The incoming object (ExpandoObject) may have 100 attributes, I only need a few attributes specified in the list (ListSearchImportFieldModel).

Who can help me out, thank you very much!

I tried to let chatgpt do it for me, but it didn’t work

Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0 
    public static Expression<Func<ExpandoObject, object>> CreateNameExpression(IEnumerable<ListSearchImportFieldModel> list){
   ParameterExpression expandoParam = Expression.Parameter(typeof(ExpandoObject), "expando");

// Create a list to store the values of the Name property
List<Expression> nameValueExpressions = new List<Expression>();

// Iterate through each object in List<ListSearchImportFieldModel> and add the value of the Name property to the list
foreach (ListSearchImportFieldModel keyModel in list)
{
    // Create a property access expression representing the access to the Name property of the KeyModel object
    Expression namePropertyAccess = Expression.Property(Expression.Constant(keyModel), "Field_Name");

    // Convert the property access expression to Object type and add the result to the list
    Expression convertedNameValue = Expression.Convert(namePropertyAccess, typeof(object));

    // Add the Name property value to the list
    nameValueExpressions.Add(convertedNameValue);
}

// Create an array initialization expression to convert the array of Name property values to properties of ExpandoObject
Expression arrayInitExpression = Expression.NewArrayInit(typeof(object), nameValueExpressions);

// Create an ExpandoObject property initialization expression
Expression expandoInitExpression = Expression.ListInit(
    Expression.New(typeof(ExpandoObject)),
    Expression.ElementInit(
        typeof(IDictionary<string, object>).GetMethod("Add"),
        Expression.Constant("NameValues"),
        arrayInitExpression
    )
);

// Create a Lambda expression with the ExpandoObject property initialization expression as the return value
Expression<Func<ExpandoObject, object>> lambda = Expression.Lambda<Func<ExpandoObject, object>>(
    expandoInitExpression,
    expandoParam
);

return lambda;

    }


  2. 0

    One could convert ExpandoObject to Dictionary and conveniently create new ExpandoObject based on just created Ditionary by simply checking keys:

    var props = new[] {"a", "b"};
var eo = new ExpandoObject();
eo.TryAdd("a", "z");
eo.TryAdd("b", "y");
eo.TryAdd("c", "x");

var dictFromEo = eo.ToDictionary(x => x.Key, x => x.Value);
var newExpando = new ExpandoObject();
Array.ForEach(props, prop =>
{
    if(dictFromEo.TryGetValue(prop, out var value))
    {
        newExpando.TryAdd(prop, value);
    }
});
    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search