CODEWITHSUNDEEP
c#reflection.net-corepropertyinfo
Dar
Dar

Reputation: 393

How to dynamically get the instance of an object's property using reflection

I have found lots of examples that ALMOST tell me what I need to know. But everything so far assumes I already have an instance of the property that I want to set the value. But I don't have an instance. I have a PropertyInfo object. I can dynamically obtain the name of the property but in order to call SetValue() I must have an instance of the property to pass to the method. How do I get an instance of the property whose value I need to set? Here is my code with ??? where an instance of the property must be provided. How do I get an instance of the property and not just a PropertyInfo object? (The reason I am writing this method is because I cannot guarantee which columns various stored procedures will return.)

protected new void MapDbResultToFields(DataRow row, DataColumnCollection columns)
{
    Console.WriteLine("Entered Clinician.MapDbResultToFields");
    var properties = this.GetType().GetProperties();
    Console.WriteLine("Properties Count: " + properties.Length);
    foreach (DataColumn col in columns)
    {
        Console.WriteLine("ColumnName: " + col.ColumnName);
    }
    foreach (var property in properties)
    {
        string propName = property.Name.ToLower();
        Console.WriteLine("Property name: " + propName);
        Console.WriteLine("Index of column name: " + columns.IndexOf(propName));
        Console.WriteLine("column name exists: " + columns.Contains(propName));
        if (columns.Contains(propName))
        {
            Console.WriteLine("PropertyType is: " + property.PropertyType);
            switch (property.PropertyType.ToString())
            {
                case "System.String":
                    String val = row[propName].ToString();
                    Console.WriteLine("RowColumn Value (String): " + val);
                    property.SetValue(???, val, null);
                    break;
                case "System.Nullable`1[System.Int64]":
                case "System.Int64":
                    Int64.TryParse(row[propName].ToString(), out var id);
                    Console.WriteLine("RowColumn Value (Int64): " + id);
                    property.SetValue(???, id, null);
                    break;
                case "System.Boolean":
                    Boolean.TryParse(row[propName].ToString(), out var flag);
                    Console.WriteLine("RowColumn Value (Boolean): " + flag);
                    property.SetValue(???, flag, null);
                    break;
            }

        }
        else
        {
            Console.WriteLine("Property name not found in columns list");
        }
    }
}

Upvotes: 1

Views: 995

Answers (2)

Jim W
Jim W

Reputation: 5026

You mistakenly believed you needed an instance of the property you were trying to set, but actually you need an instance of the object upon which you want to set the property. A property has no life outside of an object to which it belongs.

property.SetValue(this, val, null);

Is most likely what you were looking for.

Upvotes: 3

alacom
alacom

Reputation: 236

Since you are getting the properties of THIS.. you actually have an instance of the object you are trying to set. Just use the THIS keyword when you set it.

When you GET the properties like this

var properties = this.GetType().GetProperties();

You SET the properties like this

foreach(var property in properties)
{
    property.SetValue(this, id, null);
}

This will not work if you tried to get properties from an object you don't have an instance of. 

var properties = SomeObject.GetType().GetProperties();

Hopefully this answers your questions!

Cheers

Upvotes: 2

Related Questions