How to insert data into sql from combobox?

when i put only 1 combobox

Code:

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cmd = new SqlCeCommand("Insert into Art (mr) values(" + comboBox1.Text + ")", cn);

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its succesfully insert data into Art table but when i try whit 2 comboxes i got error

the data was truncated while converting from one data type to another [ Name of function(if known) = ]

if somebody know how to fix it?