How to access form methods and controls from a class in C

Question

I m working on a C  program  and right now I have one Form and a couple of classes  I would like to be able to access some of the Form controls  such as a TextBox  from my class  When I try to change the text in the TextBox from my class I get the following error      An object reference is required for the non-static field  method  or property  Project Form1 txtLog       How can I access methods and controls that are in Form1 cs from one of my classes

User · Answer

you have to have a reference to the form object in order to access its elements the elements have to be declared public in order for another class to access them don t do this - your class has to know too much about how your form is implemented  do not expose form controls outside of the form class instead  make public properties on your form to get set the values you are interested in post more details of what you want and why  it sounds like you may be heading off in a direction that is not consistent with good encapsulation practices

User · Answer

You are trying to access the class as opposed to the object  That statement can be confusing to beginners  but you are effectively trying to open your house door by picking up the door on your house plans   If you actually wanted to access the form components directly from a class  which you don t  you would use the variable that instantiates your form    Depending on which way you want to go you d be better of either sending the text of a control or whatever to a method in your classes eg  public void DoSomethingWithText string formText          do something text in here     or exposing properties on your form class and setting the form text in there - eg  string SomeProperty      get             return textBox1 Text          set            textBox1 Text   value

User · Answer

JUST YOU CAN SEND FORM TO CLASS LIKE THIS  Class1 excell   new Class1       you must declare this in form as you want to control  excel get data from excel this      And create instance for class and sen this form to another class   INSIDE CLASS AS YOU CREATE CLASS1  class Class1       public void get data from excel  Form1 form    you getting the form here and you can control as you want               form ComboBox1 text    try it     you can chance Form1 UI elements inside the class now           IMPORTANT   But you must not forgat you have declare modifier form properties as PUBLIC and you can access other wise you can not see the control in form from class

User · Answer

You need access to the object     you can t simply ask the form class      eg     you would of done some thing like  Form1 txtLog Text    blah    instead of  Form1 blah   new Form1    blah txtLog Text    hello

User · Answer

You are trying to access the class as opposed to the object  That statement can be confusing to beginners  but you are effectively trying to open your house door by picking up the door on your house plans   If you actually wanted to access the form components directly from a class  which you don t  you would use the variable that instantiates your form    Depending on which way you want to go you d be better of either sending the text of a control or whatever to a method in your classes eg  public void DoSomethingWithText string formText          do something text in here     or exposing properties on your form class and setting the form text in there - eg  string SomeProperty      get             return textBox1 Text          set            textBox1 Text   value

User · Answer

You need to make the members in the for the form class either public or  if the service class is in the same assembly  internal  Windows controls  visibility can be controlled through their Modifiers properties    Note that it s generally considered a bad practice to explicitly tie a service class to a UI class  Rather you should create good interfaces between the service class and the form class  That said  for learning or just generally messing around  the earth won t spin off its axis if you expose form members for service classes    rp

User · Answer

You need access to the object     you can t simply ask the form class      eg     you would of done some thing like  Form1 txtLog Text    blah    instead of  Form1 blah   new Form1    blah txtLog Text    hello

User · Answer

I m relatively new to c  and brand new to stackoverflow  Anyway  regarding the question on how to access controls on a form from a class  I just used the ControlCollection  Controls  class of the form             Add a new form called frmEditData to project            Draw a textbox on it named txtTest  set the text to           something in design as a test          Form frmED    new frmEditData            MessageBox Show frmED Controls  txtTest   Text     Worked for me  maybe it will be of assistance in both questions

User · Answer

JUST YOU CAN SEND FORM TO CLASS LIKE THIS  Class1 excell   new Class1       you must declare this in form as you want to control  excel get data from excel this      And create instance for class and sen this form to another class   INSIDE CLASS AS YOU CREATE CLASS1  class Class1       public void get data from excel  Form1 form    you getting the form here and you can control as you want               form ComboBox1 text    try it     you can chance Form1 UI elements inside the class now           IMPORTANT   But you must not forgat you have declare modifier form properties as PUBLIC and you can access other wise you can not see the control in form from class

User · Answer

you have to have a reference to the form object in order to access its elements the elements have to be declared public in order for another class to access them don t do this - your class has to know too much about how your form is implemented  do not expose form controls outside of the form class instead  make public properties on your form to get set the values you are interested in post more details of what you want and why  it sounds like you may be heading off in a direction that is not consistent with good encapsulation practices

User · Answer

You need to make the members in the for the form class either public or  if the service class is in the same assembly  internal  Windows controls  visibility can be controlled through their Modifiers properties    Note that it s generally considered a bad practice to explicitly tie a service class to a UI class  Rather you should create good interfaces between the service class and the form class  That said  for learning or just generally messing around  the earth won t spin off its axis if you expose form members for service classes    rp

User · Answer

You are trying to access the class as opposed to the object  That statement can be confusing to beginners  but you are effectively trying to open your house door by picking up the door on your house plans   If you actually wanted to access the form components directly from a class  which you don t  you would use the variable that instantiates your form    Depending on which way you want to go you d be better of either sending the text of a control or whatever to a method in your classes eg  public void DoSomethingWithText string formText          do something text in here     or exposing properties on your form class and setting the form text in there - eg  string SomeProperty      get             return textBox1 Text          set            textBox1 Text   value

User · Answer

You need access to the object     you can t simply ask the form class      eg     you would of done some thing like  Form1 txtLog Text    blah    instead of  Form1 blah   new Form1    blah txtLog Text    hello

User · Answer

You need access to the object     you can t simply ask the form class      eg     you would of done some thing like  Form1 txtLog Text    blah    instead of  Form1 blah   new Form1    blah txtLog Text    hello

User · Answer

you have to have a reference to the form object in order to access its elements the elements have to be declared public in order for another class to access them don t do this - your class has to know too much about how your form is implemented  do not expose form controls outside of the form class instead  make public properties on your form to get set the values you are interested in post more details of what you want and why  it sounds like you may be heading off in a direction that is not consistent with good encapsulation practices

User · Answer

Another solution would be to pass the textbox  or control you want to modify  into the method that will manipulate it as a parameter   public partial class Form1   Form       public Form1                 InitializeComponent               private void button1 Click object sender  EventArgs e                TestClass test   new TestClass            test ModifyText textBox1            public class TestClass       public void ModifyText TextBox textBox                textBox Text    New text

User · Answer

You need to make the members in the for the form class either public or  if the service class is in the same assembly  internal  Windows controls  visibility can be controlled through their Modifiers properties    Note that it s generally considered a bad practice to explicitly tie a service class to a UI class  Rather you should create good interfaces between the service class and the form class  That said  for learning or just generally messing around  the earth won t spin off its axis if you expose form members for service classes    rp

User · Answer

If the form starts up first  in the form Load handler we can instantiate a copy of our class  We can have properties that reference whichever controls we want to reference  Pass the reference to the form  this  to the constructor for the class   public partial class Form1   Form       public ListView Lv               get   return lvProcesses               public Form1                 InitializeComponent               private void Form1 Load object sender  EventArgs e                Utilities ut   new Utilities this             In your class  the reference from the form is passed into the constructor and stored as a private member  This form reference can be used to access the form s properties   class Utilities       private Form1  mainForm      public Utilities Form1 mainForm                 mainForm   mainForm           mainForm Lv Items Clear

User · Answer

Another solution would be to pass the textbox  or control you want to modify  into the method that will manipulate it as a parameter   public partial class Form1   Form       public Form1                 InitializeComponent               private void button1 Click object sender  EventArgs e                TestClass test   new TestClass            test ModifyText textBox1            public class TestClass       public void ModifyText TextBox textBox                textBox Text    New text

User · Answer

You are trying to access the class as opposed to the object  That statement can be confusing to beginners  but you are effectively trying to open your house door by picking up the door on your house plans   If you actually wanted to access the form components directly from a class  which you don t  you would use the variable that instantiates your form    Depending on which way you want to go you d be better of either sending the text of a control or whatever to a method in your classes eg  public void DoSomethingWithText string formText          do something text in here     or exposing properties on your form class and setting the form text in there - eg  string SomeProperty      get             return textBox1 Text          set            textBox1 Text   value

User · Answer

you have to have a reference to the form object in order to access its elements the elements have to be declared public in order for another class to access them don t do this - your class has to know too much about how your form is implemented  do not expose form controls outside of the form class instead  make public properties on your form to get set the values you are interested in post more details of what you want and why  it sounds like you may be heading off in a direction that is not consistent with good encapsulation practices

User · Answer

I m relatively new to c  and brand new to stackoverflow  Anyway  regarding the question on how to access controls on a form from a class  I just used the ControlCollection  Controls  class of the form             Add a new form called frmEditData to project            Draw a textbox on it named txtTest  set the text to           something in design as a test          Form frmED    new frmEditData            MessageBox Show frmED Controls  txtTest   Text     Worked for me  maybe it will be of assistance in both questions

User · Answer

Another solution would be to pass the textbox  or control you want to modify  into the method that will manipulate it as a parameter   public partial class Form1   Form       public Form1                 InitializeComponent               private void button1 Click object sender  EventArgs e                TestClass test   new TestClass            test ModifyText textBox1            public class TestClass       public void ModifyText TextBox textBox                textBox Text    New text

User · Answer

If the form starts up first  in the form Load handler we can instantiate a copy of our class  We can have properties that reference whichever controls we want to reference  Pass the reference to the form  this  to the constructor for the class   public partial class Form1   Form       public ListView Lv               get   return lvProcesses               public Form1                 InitializeComponent               private void Form1 Load object sender  EventArgs e                Utilities ut   new Utilities this             In your class  the reference from the form is passed into the constructor and stored as a private member  This form reference can be used to access the form s properties   class Utilities       private Form1  mainForm      public Utilities Form1 mainForm                 mainForm   mainForm           mainForm Lv Items Clear

User · Answer

Another solution would be to pass the textbox  or control you want to modify  into the method that will manipulate it as a parameter   public partial class Form1   Form       public Form1                 InitializeComponent               private void button1 Click object sender  EventArgs e                TestClass test   new TestClass            test ModifyText textBox1            public class TestClass       public void ModifyText TextBox textBox                textBox Text    New text

User · Answer

You need to make the members in the for the form class either public or  if the service class is in the same assembly  internal  Windows controls  visibility can be controlled through their Modifiers properties    Note that it s generally considered a bad practice to explicitly tie a service class to a UI class  Rather you should create good interfaces between the service class and the form class  That said  for learning or just generally messing around  the earth won t spin off its axis if you expose form members for service classes    rp

[c#] How to access form methods and controls from a class in C#?

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