how to display random number in textbox

Question

In Gridview record as follows
Companyid Companyname
select 1 SK
select 2 MR
When i click the first row select button in gridview display the record as follows
Companyid 1 (textbox1)
companyname SK (textbox2)

I want to display random number in companyname in textbox2.
for example in textbox2 i want to display random number SK99059
for example i mentioning random number 99059.

how to display random number in textbox2.

for that how can i do in asp.net using c#