Hi selverca,

Please refer below sample.

SQL

CREATE TABLE [Projects]
( 
    [ID] INT IDENTITY,
	[Prosjektnummer] VARCHAR (20),
	[aktiv] VARCHAR (20),
	[PI_bnava] VARCHAR (20),
)

INSERT INTO [Projects] VALUES('123','False','User1')
INSERT INTO [Projects] VALUES('789','False','User5')
INSERT INTO [Projects] VALUES('456','False','User1')
INSERT INTO [Projects] VALUES('123','False','User1')


SELECT * FROM [Projects]
DROP TABLE [Projects]

HTML

<table>
    <tr>
        <td>UserName:</td>
        <td>
            <asp:TextBox ID="txtusername" runat="server" />
        </td>
    </tr>
    <tr>
        <td></td>
        <td>
            <asp:Button ID="btnlogin" Text="Login" runat="server" OnClick="Login" />
        </td>
    </tr>
</table>
<asp:Repeater ID="rptDetails" runat="server">
    <HeaderTemplate>
        <table>
            <tr>
                <td></td>
                <td>Id</td>
                <td>Proshektnummer</td>
                <td>Prosjektnavn</td>
                <td>prosjektbeskrivelse</td>
                <td></td>
            </tr>
    </HeaderTemplate>
    <ItemTemplate>
        <tr>
            <td>
                <asp:CheckBox ID="chkBox" runat="server" /></td>
            <td>
                <asp:Label ID="lblId" Text='<%#Eval("Id") %>' runat="server" />
            </td>
            <td>
                <asp:Label ID="lblProshektnummer" Text='<%#Eval("Proshektnummer") %>' runat="server" />
            </td>
            <td>
                <asp:Label ID="lblProsjektnavn" Text='<%#Eval("Prosjektnavn") %>' runat="server" />
            </td>
            <td>
                <asp:Label ID="lblprosjektbeskrivelse" Text='<%#Eval("prosjektbeskrivelse") %>' runat="server" />
            </td>
        </tr>
    </ItemTemplate>
    <FooterTemplate>
        </table>
    </FooterTemplate>
</asp:Repeater> 

Namespaces

C#

using System.Data;
using System.Data.SqlClient;
using System.Configuration;

VB.Net

Imports System.Data
Imports System.Data.SqlClient
Imports System.Configuration

Code

C#

protected void Login(object sender, EventArgs e)
{
    string loginUser = txtusername.Text;
    DataTable dt = new DataTable();
    dt.Columns.AddRange(new DataColumn[4] {
                        new DataColumn("Id"),
                        new DataColumn("Proshektnummer"),
                        new DataColumn("Prosjektnavn"),
                        new DataColumn("prosjektbeskrivelse")});
    dt.Rows.Add("1", "123", "Testing1", "Database");
    dt.Rows.Add("2", "456", "Testing2", "Database");
    dt.Rows.Add("3", "789", "Testing3", "Database");
    dt.Rows.Add("4", "555", "Testing4", "Database");
    rptDetails.DataSource = dt;
    rptDetails.DataBind();


    string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(conString))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT * FROM Projects", con))
        {
            using (SqlDataAdapter sda = new SqlDataAdapter(cmd))
            {
                DataTable dt1 = new DataTable();
                sda.Fill(dt1);
                DataRow[] dr = dt1.Select("PI_bnava='" + loginUser + "'");

                foreach (RepeaterItem item in rptDetails.Items)
                {
                    Label pNo = item.FindControl("lblProshektnummer") as Label;
                    CheckBox isLogin = item.FindControl("chkBox") as CheckBox;
                    List<DataRow> result = dr.AsEnumerable().Where(x => x["Prosjektnummer"].ToString() == pNo.Text).ToList();
                    isLogin.Checked = result.Count > 0;
                }
            }
        }
    }
}

VB.Net

Protected Sub Login(ByVal sender As Object, ByVal e As EventArgs)
    Dim loginUser As String = txtusername.Text
    Dim dt As DataTable = New DataTable()
    dt.Columns.AddRange(New DataColumn(3) {New DataColumn("Id"),
                                           New DataColumn("Proshektnummer"),
                                           New DataColumn("Prosjektnavn"),
                                           New DataColumn("prosjektbeskrivelse")})
    dt.Rows.Add("1", "123", "Testing1", "Database")
    dt.Rows.Add("2", "456", "Testing2", "Database")
    dt.Rows.Add("3", "789", "Testing3", "Database")
    dt.Rows.Add("4", "555", "Testing4", "Database")
    rptDetails.DataSource = dt
    rptDetails.DataBind()
    Dim conString As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(conString)
        Using cmd As SqlCommand = New SqlCommand("SELECT * FROM Projects", con)
            Using sda As SqlDataAdapter = New SqlDataAdapter(cmd)
                Dim dt1 As DataTable = New DataTable()
                sda.Fill(dt1)
                Dim dr As DataRow() = dt1.[Select]("PI_bnava='" & loginUser & "'")
                For Each item As RepeaterItem In rptDetails.Items
                    Dim pNo As Label = TryCast(item.FindControl("lblProshektnummer"), Label)
                    Dim isLogin As CheckBox = TryCast(item.FindControl("chkBox"), CheckBox)
                    Dim result As List(Of DataRow) = dr.AsEnumerable().Where(Function(x) x("Prosjektnummer").ToString() = pNo.Text).ToList()
                    isLogin.Checked = result.Count > 0
                Next
            End Using
        End Using
    End Using
End Sub

Screenshot