Proper Way to Initialize a C# Dictionary with Values
I Am Creating a Dictionary in a C# File with the Following Code: Private Readonly Dictionary File_Type_Dict = New Dictionary { {"Csv", Xlfileformat. xlCSV}...
I am creating a dictionary in a C# file with the following code:
private readonly Dictionary<string, XlFileFormat> FILE_TYPE_DICT
= new Dictionary<string, XlFileFormat>
{
{"csv", XlFileFormat.xlCSV},
{"html", XlFileFormat.xlHtml}
};
There is a red line under new with the error:
Feature 'collection initilializer' cannot be used because it is not part of the ISO-2 C# language specification
What is going on here?
I am using .NET version 2.
I can't reproduce this issue in a simple .NET 4.0 console application:
static class Program
{
static void Main(string[] args)
{
var myDict = new Dictionary<string, string>
{
{ "key1", "value1" },
{ "key2", "value2" }
};
Console.ReadKey();
}
}
Can you try to reproduce it in a simple Console application and go from there? It seems likely that you're targeting .NET 2.0 (which doesn't support it) or client profile framework, rather than a version of .NET that supports initialization syntax.
With C# 6.0, you can create a dictionary in the following way:
var dict = new Dictionary<string, int>
{
["one"] = 1,
["two"] = 2,
["three"] = 3
};
It even works with custom types.
You can initialize a Dictionary (and other collections) inline. Each member is contained with braces:
Dictionary<int, StudentName> students = new Dictionary<int, StudentName>
{
{ 111, new StudentName { FirstName = "Sachin", LastName = "Karnik", ID = 211 } },
{ 112, new StudentName { FirstName = "Dina", LastName = "Salimzianova", ID = 317 } },
{ 113, new StudentName { FirstName = "Andy", LastName = "Ruth", ID = 198 } }
};
See How to initialize a dictionary with a collection initializer (C# Programming Guide) for details.
Suppose we have a dictionary like this:
Dictionary<int, string> dict = new Dictionary<int, string>();
dict.Add(1, "Mohan");
dict.Add(2, "Kishor");
dict.Add(3, "Pankaj");
dict.Add(4, "Jeetu");
We can initialize it as follows.
Dictionary<int, string> dict = new Dictionary<int, string>
{
{ 1, "Mohan" },
{ 2, "Kishor" },
{ 3, "Pankaj" },
{ 4, "Jeetu" }
};
Object initializers were introduced in C# 3.0. Check which framework version you are targeting.
Note that C# 9 allows Target-typed new expressions so if your variable or a class member is not abstract class or interface type duplication can be avoided:
private readonly Dictionary<string, XlFileFormat> FILE_TYPE_DICT = new ()
{
{ "csv", XlFileFormat.xlCSV },
{ "html", XlFileFormat.xlHtml }
};
With ะก# 6.0
var myDict = new Dictionary<string, string>
{
["Key1"] = "Value1",
["Key2"] = "Value2"
};
The code looks fine. Just try to change the .NET framework to v2.0 or later.
Elena Rostova holds a Master's degree in Public Health Journalism. She covers groundbreaking medical research, holistic wellness trends, mental health awareness, and nutritional science.
