Error In Declaring Data Type

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ASP.NET

Hi frnds...
Am Creating an application which the database table is created dynamically the thing is now i need to change my data type varchar(max) to int also to set an primary key and Auto incremnt the value pls do guide me...I got an error as

In Correct Syntax near Int32

Here is my code

foreach (DataColumn dc in dt.Columns)
               {
                   if (exists == null)
                   {
                       SqlCommand createtable = new SqlCommand("CREATE TABLE " + TextBox1.Text + " (" + TextBox1.Text.Substring(0, 1) + "ID" + " sizeof(Int32) )", con);
                       createtable.ExecuteNonQuery();
                       exists = dt.TableName;
                   }

               }


               SqlCommand addcolumn = new SqlCommand("ALTER TABLE " + TextBox1.Text + " ADD " + TextBox2.Text + " varchar(MAX)," + TextBox3.Text + " varchar(MAX) ," + TextBox4.Text + " varchar(MAX)," + TextBox5.Text + " varchar(MAX)," + TextBox6.Text + " varchar(MAX)," + TextBox7.Text + " varchar(MAX)," + TextBox8.Text + " varchar(MAX)", con);
               addcolumn.ExecuteNonQuery();
               Session["tablename"] = TextBox1.Text.ToString();

               break;

Thank You..,