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;
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.
Use SizeMode on the TabControl: http://msdn.microsoft.com/en-us/library/system.windows.forms.tabcontrol.sizemode.aspx
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