问题
I have a TabControl with two tab pages.

How can I make the tab pages fit into the width of the TabControl like shown in the below screenshot.

I tried with the following line of code but it does not work either.
tabControl1.SizeMode = TabSizeMode.FillToRight;
回答1:
First, set your tabControl1 size mode:
tabControl1.SizeMode = TabSizeMode.Fixed;
Then you have to recalculate width of the tab page header:
tabControl1.ItemSize = new Size(tabControl1.Width / tabControl1.TabCount, 0);
Pay attention: 1. value 0 means that height will be default. 2. Recalculate item size after you had added tab page to tab control. Consider what happens when you resize the control.
回答2:
Use SizeMode on the TabControl: http://msdn.microsoft.com/en-us/library/system.windows.forms.tabcontrol.sizemode.aspx
回答3:
this is illegal way to solve this kind of issue
Increase the padding (X,Y) X 100 // represent some allowed figures Y 3 // represent some allowed figure.
来源:https://stackoverflow.com/questions/13305457/how-to-make-tab-pages-widths-fit-into-the-tabcontrols-width