error: string must be exactly one character long

hi all, i'm retreiving user input using textboxes and saving to a gridview. i'm getting this error and i dont know whats causing it.

<asp:SqlDataSourceID="SqlDataSource1"runat="server"

InsertCommand="INSERT INTO test101(Surname,Names,Regno)VALUES (@.Surname, @.Names, @.Regno)"

ConnectionString="<%$ ConnectionStrings:engineeringConnectionString %>"ProviderName=System.Data.SqlClient

ConflictDetection="CompareAllValues">

<InsertParameters>

<asp:ControlParameterControlID="TextBox1"DefaultValue="TextBox1.Text"Name="Surname"

PropertyName="Text"Size="50"Type=Char/>

<asp:ControlParameterControlID="TextBox2"DefaultValue="TextBox2.Text"Name="Names"

PropertyName="Text"Size="50"Type=Char/>

<asp:ParameterDefaultValue="TextBox3.Text"Name="Regno"/>

</InsertParameters>

</asp:SqlDataSource>

<asp:GridViewID="GridView1"

runat="server"AutoGenerateColumns="False"AutoGenerateDeleteButton="True"DataKeyNames="ID"

AutoGenerateEditButton="True"AllowSorting="True"BackColor="LightGoldenrodYellow"

BorderColor="Tan"BorderWidth="1px"CellPadding="2"ForeColor="Black"GridLines="None"PageSize="20"

Height="374px"EmptyDataText="null"DataSourceID=SqlDataSource1Visible="False">

<Columns>

<asp:BoundFieldDataField="ID"HeaderText="ID"InsertVisible="False"ReadOnly="True"

SortExpression="ID"/>

<asp:BoundFieldDataField="Surname"HeaderText="Surname"SortExpression="Surname"/>

<asp:BoundFieldDataField="Names"HeaderText="Names"SortExpression="Names"/>

<asp:BoundFieldDataField="Registration"HeaderText="Registration"SortExpression="Registration"/>

<asp:BoundFieldDataField="Grade"HeaderText="Grade"SortExpression="Grade"/>

</Columns>

</asp:GridView>

and the code behind is:

protectedvoid Page_Load(object sender,EventArgs e)

{

SqlConnection conn =newSqlConnection("Data Source=(local);Initial Catalog=engineering; Integrated Security=True");

conn.Open();

GridView1.DataBind();

conn.Close();

}

publicvoid login1_Click(object sender,EventArgs e)

{

SqlDataSource1.Insert();

Response.Write("you have successfully being added to the database");

can anyone help?!!!

Check out this link:http://vbcity.com/forums/topic.asp?tid=148073

Good luck.