- \n
- Pass the data from Controller to View.
<\/li>\n\n\n\n - Pass the data from an action to another action in Controller.
<\/li>\n\n\n\n - Pass the data in between Controllers.
<\/li>\n\n\n\n - Pass the data between consecutive requests.<\/li>\n<\/ol>\n<\/div>\n\n\n
What is Dictionary Object?<\/h2>\n\n\n\n
In C#, Dictionary is used to store the key-value pairs. The Dictionary is the same as the non-generic hashtable. It can be defined under System.Collection.Generic namespace. It has a dynamic nature which means the size of the dictionary grows according to the need.<\/p>\n\n\n\n
Here is an example:<\/p>\n\n\n\n
using System;\nusing System.Collections.Generic; \n \nclass Demo {\n \n static public void Main () {\n \n Dictionary<int, string> My_dict1 = \n new Dictionary<int, string>(); \n \n My_dict1.Add(1123, \"Welcome\");\n My_dict1.Add(1124, \"to\");\n My_dict1.Add(1125, \"Programming\");\n \n foreach(KeyValuePair<int, string> ele1 in My_dict1)\n {\n Console.WriteLine(\"{0} and {1}\",\n ele1.Key, ele1.Value);\n }\n Console.WriteLine();\n \n Dictionary<string, string> My_dict2 = \n new Dictionary<string, string>(){\n {\"a.1\", \"Dog\"},\n {\"a.2\", \"Cat\"},\n {\"a.3\", \"Pig\"} }; \n \n foreach(KeyValuePair<string, string> ele2 in My_dict2)\n {\n Console.WriteLine(\"{0} and {1}\", ele2.Key, ele2.Value);\n }\n }\n}<\/pre>\n\n\n\nWhat is ViewData?<\/h2>\n\n\n\n
In MVC, when we want to transfer the data from the controller to view, we use ViewData. It is a dictionary type that stores the data internally.<\/p>\n\n\n\n
ViewData contains key-value pairs which means each key must be a string in a dictionary.<\/p>\n\n\n\n
The only limitation of ViewData is, it can transfer data from controller to view. It can not transfer in any other way and it is valid only during the current request.<\/p>\n\n\n\n
Syntax:<\/p>\n\n\n\n
public ViewDataDictionary ViewData { get; set; }<\/pre>\n\n\n\nWhen we want to use the key-value pair to ViewData,<\/p>\n\n\n\n
ViewData[\"DemoText\u201d]=\"This is syntax.\";<\/pre>\n\n\n\n
We can also use ViewData in the razor view from controller. Here is the syntax for that:<\/p>\n\n\n\n
<h1>@ViewData[\"PageTtitle\"]<\/h1><\/pre>\n\n\n\n
When we want to add custom objects, array, list, etc, in ViewData, and cast them back in the View. We can use the code snippet as below:<\/p>\n\n\n\n
public ActionResult actionViewData()\n{\nArrayList alCit\ny = new ArrayList();\nalCity.Add(\"Ahmedabad\");\nalCity.Add(\"Rajkot\");\nalCity.Add(\"Amreli\");\nalCity.Add(\"Bhavnagar\");\nalCity.Add(\"Surat\");\nalCity.Add(\"Junagadh\");\nalCity.Add(\"Vadodara\");\nViewData[\"City\"] = alCity;\nreturn View();\n}<\/pre>\n\n\n\n@{\nArrayList _city = ViewData[\"City\"] as ArrayList;\n foreach (string city in _city)\n {\n <div>@city<\/div>\n }\n}<\/pre>\n\n\n\n![\"\"](\"https:\/\/www.red-gate.com\/simple-talk\/wp-content\/uploads\/2021\/09\/word-image-1.png\")
<\/figure>\n\n\n\n<\/p>\n\n\n\n
Figure 1: ViewData Flow<\/p>\n\n\n\n
Here is an example of ViewData which shows how to transfer data from controller to view using ViewData.<\/p>\n\n\n\n
public ActionResult Index()\n{\t\n IList<Employee> employeeList = new List<Employee>();\n employeeList.Add(new Employee(){ EmployeeName = \"Hemanshu\" });\n employeeList.Add(new Employee(){ EmployeeName = \"Harsh\" });\n employeeList.Add(new Employee(){ EmployeeName = \"Hiren\" });\n ViewData[\"employees\"] = employeeList;\n \n return View();\n}<\/pre>\n\n\n\nIn this example, ViewData[\u201cemployees\u201d] is assigned to an employeeList where \u201cemployees\u201d is a key and employeeList is a value.<\/p>\n\n\n\n
To access the ViewData[\u201cemployees\u201d] in the view, here is the snippet of code you can use.<\/p>\n\n\n\n
<ul>\n@foreach (var std in ViewData[\"employees\"] as IList<Employee>)\n{\n <li>\n @emp.EmployeeName\n <\/li>\n}\n<\/ul><\/pre>\n\n\n\nIn simple terms, these are the ways to store and retrieve data to and for respectively ViewData as shown:<\/p>\n\n\n\n
Storing :<\/p>\n\n\n\n
ViewData[\u201cemployees\u201d] = employeeList;<\/pre>\n\n\n\n
Retriving :<\/p>\n\n\n\n
string employee = ViewData[\u201cEmployee\u201d].ToString();<\/pre>\n\n\n\n
<\/p>\n\n\n\n
In MVC, ViewData does not check compile-time errors. If we misspell the key names, we would not get any errors but we can identify them at the run time.<\/p>\n\n\n\n
For example,<\/p>\n\n\n\n
Controller:<\/p>\n\n\n\n
using System.Collections.Generic;\nusing System.Web.Mvc;\nnamespace DemoMvcApplication.Controllers{\n public class HomeController : Controller{\n public ViewResult Index(){\n ViewData[\"Countries\"] = new List<string>{\n \"India\",\n \"Malaysia\",\n \"Dubai\",\n \"USA\",\n \"UK\"\n };\n return View();\n }\n }\n}<\/pre>\n\n\n\nView<\/p>\n\n\n\n
@{\n ViewBag.Title = \"Countries List\";\n}\n<h2>Countries List<\/h2>\n<ul>\n@foreach(string country in (List<string>)ViewData[\"Countries\"]){\n <li>@country<\/li>\n}\n<\/ul><\/pre>\n\n\n\n![\"\"](\"https:\/\/www.red-gate.com\/simple-talk\/wp-content\/uploads\/2021\/09\/word-image.jpeg\")
<\/figure>\n\n\n\n
![\"ASP](\"https:\/\/www.red-gate.com\/simple-talk\/wp-content\/uploads\/2021\/09\/asp-view-bag-2.png\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/www.red-gate.com\/simple-talk\/wp-content\/uploads\/2021\/09\/word-image-2.png\")
<\/figure>\n\n\n\n