Input String Was Not In A Correct Format.

Hi i keep getting an error when i search based on the coachname textbox or the team name dropdown list, when I search based on the region dropdown list it works fine. The error i get is "Input string was not in a correct format"

Here is my code;

 protected void Button1_Click(object sender, EventArgs e)
{

if (this.IsValid)
{

lblResults.Text = "Here are the search results!";
}

SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["streamConnectionString"].ConnectionString);
conn.Open();

SqlCommand command = new SqlCommand("stream_FindTeam", conn);
command.CommandType = CommandType.StoredProcedure;

command.Parameters.Add("@coachName", SqlDbType.VarChar, 250).Value = coachName.Text;command.Parameters.Add("@TeamName", SqlDbType.VarChar, 250).Value = TeamList.SelectedValue;
{

if ((string.IsNullOrEmpty(Region.SelectedValue)))
{

command.Parameters.Add("@regionID", DBNull.Value);
}

else

{

command.Parameters.Add("@regionID", SqlDbType.Int ).Value = Region.SelectedValue;
}

}

SqlDataReader reader = command.ExecuteReader();
DataList1.DataSource = reader;

DataList1.DataBind();

conn.Close();

}

protected void DataList1_SelectedIndexChanged(object sender, EventArgs e)
{

}

protected void CustomValidator1_ServerValidate(object source, ServerValidateEventArgs args)
{

args.IsValid = !(String.IsNullOrEmpty(coachName.Text) && TeamList.SelectedIndex == 0 && Region.SelectedIndex == 0);
}

}



 And my stored procedure is ALTER PROCEDURE [dbo].[stream_FindTeam]
@coachName varchar(100),
@TeamName varchar(100),
@regionID INT
AS
SELECT TeamID, coachName FROM Teams
WHERE coachName LIKE COALESCE(@coachName, coachName)
AND TeamName = COALESCE(@TeamName, TeamName)
AND regionID = COALESCE(@regionID, regionID);