Error in updating products on datagridview c#

Question

I got this error below while trying to update product table:

 

Unclosed quotation mark after the character string " where ProID=''. Incorrect syntax near "where ProID =''.

 

My codes:

private void btnUpdate_Click(object sender, EventArgs e)
{
try
{
con.Open();
cmd = new SqlCommand("UPDATE tbl_Products SET ProName='" +txtProName.Text+"' where ProID='"+txtProID.Text+"' ", con);
cmd.ExecuteNonQuery();
con.Close();
MessageBox.Show("Product Info Saved...");
fillGrid();
cleartext();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
con.Close();
{
}
}
private void cleartext()
{
txtProID.Text = "";
txtProName.Text = "'";
}
}
}

Please help me find the unclosed quotation

thanks