Failed To Enable Constraints

I have to admit I'm pretty new to ASP.net.

I'm trying to insert a row of data into my SQLExpress database table "Prets"

I'm getting the user_ID from the table "Membres"

Here's the code I have:

Imports System.Web.UI.Page
Imports System.Security.Principal
Imports WiseNetTableAdapters

Partial Class membre_sec_Pret_demande_pret
    Inherits System.Web.UI.Page

    Protected Sub submit_btn_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles submit_btn.Click
        Dim User As String = My.User.Name
        Dim pretAdapter As New PretsTableAdapter
        Dim membreAdapter As New MembresTableAdapter
        pretAdapter.AjouterPret(Convert.ToInt32(membreAdapter.GetUserIDbyName(User)), Convert.ToDecimal(montant_txt.Text), Convert.ToString(raison_txt.Text))
    End Sub
End Class


And here's the error I get at runtime:
Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Data.ConstraintException: Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.

Source Error:





Line 1610: }
Line 1611: WiseNet.MembresDataTable dataTable = new WiseNet.MembresDataTable();
Line 1612: this.Adapter.Fill(dataTable);
Line 1613: return dataTable;
Line 1614: }
Source File: c:WINDOWSMicrosoft.NETFrameworkv2.0.50727Temporary ASP.NET Fileswisenetindustriesafc388c716067f12App_Code.tyietv41.0.cs    Line: 1612

Stack Trace:





[ConstraintException: Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.]
System.Data.DataTable.EnableConstraints() +1820725
System.Data.DataTable.set_EnforceConstraints(Boolean value) +39
System.Data.DataTable.EndLoadData() +138
System.Data.Common.DataAdapter.FillFromReader(DataSet dataset, DataTable datatable, String srcTable, DataReaderContainer dataReader, Int32 startRecord, Int32 maxRecords, DataColumn parentChapterColumn, Object parentChapterValue) +218
System.Data.Common.DataAdapter.Fill(DataTable[] dataTables, IDataReader dataReader, Int32 startRecord, Int32 maxRecords) +318
System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) +221
System.Data.Common.DbDataAdapter.Fill(DataTable[] dataTables, Int32 startRecord, Int32 maxRecords, IDbCommand command, CommandBehavior behavior) +162
System.Data.Common.DbDataAdapter.Fill(DataTable dataTable) +107
WiseNetTableAdapters.MembresTableAdapter.GetUserIDbyName(String nom) in c:WINDOWSMicrosoft.NETFrameworkv2.0.50727Temporary ASP.NET Fileswisenetindustriesafc388c716067f12App_Code.tyietv41.0.cs:1612
membre_sec_Pret_demande_pret.submit_btn_Click(Object sender, EventArgs e) in c:inetpubwwwrootWiseNetIndustriesmembre_secPretdemande_pret.aspx.vb:12
System.Web.UI.WebControls.Button.OnClick(EventArgs e) +105
System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +107
System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +7
System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +11
System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +33
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5102