Challenge manipulating combobox selectedvalue and selectedvaluechanged

[highjo]

Hi! i know people have asked a lot about comboboxes but it's not really about how to get the value or index or whatever.Let me explain.it's users access management application with users, roles and rights: i have a form editRight with 2 combobox cmbUsers to list users and cmbroles to list role of each users and 3 listboxes.let's pause here on load event i fill users combobox with users private void EditRight_Load(object sender, EventArgs e) { try { //Load the user list in the dt_users dataset.dt_users and dt_roles are declare as global variables dt_users = UserManager.FindAll().Tables[0]; //set the combobox cmbUsers datasource cmbUsers.DataSource = dt_users.DefaultView; //set display member and value member cmbUsers.DisplayMember = "user_name"; cmbUsers.ValueMember = "user_id"; CallFillRoleCombo((int)cmbUsers.SelectedValue); } catch (System.Exception ex) { MessageBox.Show(ex.Message); } } private void CallFillRoleCombo(int uid) { try { //load users roles into dt_roles database dt_roles = UserRoleManager.FindByUser(uid).Tables[0]; //set combobox datasource cmbroles.DataSource = dt_roles.DefaultView; cmbroles.DisplayMember = dt_roles.Columns[2].ToString(); cmbroles.ValueMember = dt_roles.Columns[1].ToString(); } catch (System.Exception ex) { MessageBox.Show(ex.Message); } } private void cmbUsers_SelectedValueChanged(object sender, EventArgs e) { CallFillRoleCombo((int)cmbUsers.SelectedValue); } when i run the code its throws exception:Object reference not set to an instance of an object.It seems that its calling the cmbUsers_SelectedValueChanged eventhandler when setting the display member of the cmbUsers combobox. How to work around it?Thank you for reading this.

eager to learn

[Cracked Down]

In the following code for loading data in user combobox unsubscribe the event cmbUsers_SelectedValueChanged and after filling data subscribe again

private void EditRight_Load(object sender, EventArgs e)
{
try
{
//Load the user list in the dt_users dataset.dt_users and dt_roles are declare as global variables
dt_users = UserManager.FindAll().Tables[0];
//set the combobox cmbUsers datasource
cmbUsers.DataSource = dt_users.DefaultView;
//set display member and value member
cmbUsers.DisplayMember = "user_name";
cmbUsers.ValueMember = "user_id";

CallFillRoleCombo((int)cmbUsers.SelectedValue);
}
}

hope this works for you!

[Xmen Real]

got your problem try this

private void cmbUsers_SelectedValueChanged(object sender, EventArgs e)
{
if (comboBox2.SelectedValue.GetType() == typeof(int))
CallFillRoleCombo((int)cmbUsers.SelectedValue);
}

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[highjo]

Thanks guys for replying this post.Really apreciated it.The method that worked for me is the one suggested by deep@Pune.Thanks

eager to learn

[Cracked Down]

your most welcome!! :) :) yersterday I forgot to include actual lines in the code to subscribe and unsubscribe the event!! :) soru for that!!!!!