Snippet code of BindToDataTable.aspx file

<ISWebCombo:WebCombo ID="WebCombo1" runat="server" UseDefaultStyle="True"     Width="477px" Height="20px"
    DataTextField="FirstName" DataValueField="EmployeeID"
    OnInitializeDataSource="WebCombo1_InitializeDataSource">
    <Columns>
        <ISWebCombo:WebComboColumn BaseFieldName="FirstName"
            Bound="True" HeaderText="FirstName" Name="FirstName"
            Width="100px" />
        <ISWebCombo:WebComboColumn BaseFieldName="LastName"
            Bound="True" HeaderText="LastName" Name="LastName" />
        <ISWebCombo:WebComboColumn BaseFieldName="Title"
            Bound="True" HeaderText="Title" Name="Title"
            Width="200px" />
    </Columns>
    <LayoutSettings ComboMode="MultipleColumns" TextBoxMode="ReadOnly">
    </LayoutSettings>
</ISWebCombo:WebCombo>

Snippet code of BindToDataTable.aspx.cs

protected void WebCombo1_InitializeDataSource(object sender,
    ISNet.WebUI.WebCombo.DataSourceEventArgs e)
{
    DataTable dt = new DataTable();
    dt.Columns.Add(new DataColumn("EmployeeID", typeof(int)));
    dt.Columns.Add(new DataColumn("FirstName", typeof(string)));
    dt.Columns.Add(new DataColumn("LastName", typeof(string)));
    dt.Columns.Add(new DataColumn("Title", typeof(string)));
    for (int i = 0; i < 5; i++)
    {
        DataRow dr = dt.NewRow();
        dr["EmployeeID"] = i;
        dr["FirstName"] = "John" + i;
        dr["LastName"] = "Doe" + i;
        dr["Title"] = "Owner";
        dt.Rows.Add(dr);
    }
    e.DataSource = dt;
}

As shown in the above snippet code, I have a simple sample of WebCombo where the DataSource is set to a DataTable on InitializeDataSource event.

In order to set a value of WebCombo, I simply add following line in the code behind (where value property of WebCombo is set to the id property of the DataTable).

WebCombo1.Value = "3";

I’m able to see a value selected in the WebCombo.

Please feel free to let us know whether this helps or not.