{"id":17071,"date":"2022-10-23T01:06:22","date_gmt":"2022-10-22T19:36:22","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-accessing-controls-from-different-forms\/"},"modified":"2022-10-23T01:06:22","modified_gmt":"2022-10-22T19:36:22","slug":"solved-accessing-controls-from-different-forms","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-accessing-controls-from-different-forms\/","title":{"rendered":"[Solved] Accessing controls from different forms"},"content":{"rendered":"

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Looking at the original code, there are two potential reasons for the NullReferenceException<\/code> you are getting. First, tb<\/code> is not defined in the code you provide so I am not sure what that is.<\/p>\n

Secondly, TextBox textbox = form.Controls[\"textboxMain\"] as TextBox<\/code> can return null<\/code> if the control is not found or<\/em> is not a TextBox<\/code>. Controls, by default, are marked with the private<\/code> accessor, which leads me to suspect that form.Controls[...]<\/code> will return null<\/code> for private<\/code> members.<\/p>\n

While marking the controls as internal<\/code> will potentially fix this issue, it’s really not the best way to tackle this situation and will only lead to poor coding habits in the future. private<\/code> accessors on controls are perfectly fine.<\/p>\n

A better way to share the data between the forms would be with public<\/code> properties. For example, let’s say you have a TextBox<\/code> on your main screen called usernameTextBox<\/code> and want to expose it publicly to other forms:<\/p>\n

public string Username\n{\n  get { return usernameTextBox.Text; }\n  set { usernameTextBox.Text = value; }\n}\n<\/code><\/pre>\n
Then all you would have to do in your code is:<\/p>\n
var form = new MainForm();\nmyTextBox.Text = form.Username; \/\/ Get the username TextBox value\nform.Username = myTextBox.Text; \/\/ Set the username TextBox value\n<\/code><\/pre>\n
The great part about this solution is that you have better control of how data is stored via properties. Your get<\/code> and set<\/code> actions can contain logic, set multiple values, perform validation, and various other functionality.<\/p>\n
If you are using WPF<\/em> I would recommend looking up the MVVM<\/em> pattern as it allows you to do similar with object states.<\/p>\n<\/p><\/div>\n
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solved Accessing controls from different forms <\/p>\n","protected":false},"excerpt":{"rendered":"
[ad_1] Looking at the original code, there are two potential reasons for the NullReferenceException you are getting. First, tb is not defined in the code you provide so I am not sure what that is. Secondly, TextBox textbox = form.Controls[“textboxMain”] as TextBox can return null if the control is not found or is not a … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[324,2439,959],"class_list":["post-17071","post","type-post","status-publish","format-standard","hentry","category-solved","tag-c","tag-controls","tag-winforms"],"yoast_head":"\n[Solved] Accessing controls from different forms - JassWeb<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/jassweb.com\/solved\/solved-accessing-controls-from-different-forms\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] Accessing controls from different forms - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] Looking at the original code, there are two potential reasons for the NullReferenceException you are getting. First, tb is not defined in the code you provide so I am not sure what that is. Secondly, TextBox textbox = form.Controls["textboxMain"] as TextBox can return null if the control is not found or is not a ... 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First, tb is not defined in the code you provide so I am not sure what that is. Secondly, TextBox textbox = form.Controls[\"textboxMain\"] as TextBox can return null if the control is not found or is not a ... 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