OUTPUT Paramater From Stocked Procedure Sent To SDS Not Working

Juste have fun with the following, if you can manage this out your my savior, been wasting far too much time on it, tried a couple of method and none ever worked.


Conversion from type 'DBNull' to type 'String' is not valid.



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.InvalidCastException: Conversion from type 'DBNull' to type 'String' is not valid.
Source Error:





Line 105:
Line 106: Protected Sub sdsProprActionAJO_Inserted(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.SqlDataSourceStatusEventArgs) Handles sdsProprActionAJO.Inserted
Line 107: Dim MessageSysteme As String = CType((CType(e.Command.Parameters("SQL_MSG"), IDbDataParameter)).Value, String)
Line 108: End Sub
Line 109: 
         With sdsProprActionAJO
            .ConnectionString = ConfigurationManager.AppSettings("DB_CS_MSSQL")

            .InsertCommandType = SqlDataSourceCommandType.StoredProcedure
            .InsertCommand = "dbo.sp_adm_cartListe"

            .InsertParameters.Clear()
            .InsertParameters.Add("Mode", TypeCode.String, "SEL")
            .InsertParameters.Add("LPR_Groupe", TypeCode.String, CBool(CType(Me.pnlProprActionAJO.FindControl("rblProprActionAJOGroupe"), RadioButtonList).SelectedValue))
            .InsertParameters.Add("LPR_Etiquette", TypeCode.String, CType(Me.pnlProprActionAJO.FindControl("tbProprActionAJOEtiquette"), TextBox).Text)

            .Insert()
        End With
    End Sub

    Protected Sub sdsProprActionAJO_Inserted(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.SqlDataSourceStatusEventArgs) Handles sdsProprActionAJO.Inserted
        Dim MessageSysteme As String = CType((CType(e.Command.Parameters("SQL_MSG"), IDbDataParameter)).Value, String)
    End Sub

    Protected Sub sdsProprActionAJO_Inserting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.SqlDataSourceCommandEventArgs) Handles sdsProprActionAJO.Inserting
        Dim Param As System.Data.SqlClient.SqlParameter = New System.Data.SqlClient.SqlParameter()
        param.DbType = DbType.String
        param.Direction = ParameterDirection.Output
        param.ParameterName = "SQL_MSG"

        e.Command.Parameters.Add(Param)
    End Sub
 CREATE PROCEDURE [dbo].[sp_Adm_Proprietes_AJO]
(
@MODE        VARCHAR(3),
@LPR_Groupe        BIT = NULL,
@LPR_Etiquette    NVARCHAR(32) = NULL,
@RPP_LPR_IdParent    [INT] = NULL,
@RPP_LPR_IdEnfant    [INT] = NULL,
@SQL_MSG        NVARCHAR(8)  OUTPUT
)

AS
--

DECLARE @SQL_TEMP NVARCHAR(4000)
DECLARE @INT_TEMP [INT]

--

IF @MODE = 'RRP'
BEGIN
    INSERT INTO t__REL__PropParent_PropEnfant (
        RPP_LPR_IdParent,
        RPP_LPR_IdEnfant
    ) VALUES (
        @RPP_LPR_IdParent,
        @RPP_LPR_IdEnfant
    )
END

--


IF @MODE = 'LPR'
BEGIN
    IF NOT @LPR_Etiquette = NULL
        BEGIN
        SELECT * FROM t_Lib_Proprietes  WHERE (LPR_Groupe = @LPR_Groupe ) AND (LPR_Etiquette = @LPR_Etiquette )
    
        IF @@ROWCOUNT <= 0
        BEGIN
            INSERT INTO t_Lib_Proprietes (
                LPR_Groupe,
                LPR_Etiquette
            ) VALUES (
                @LPR_Groupe,
                @LPR_Etiquette
            )
            SET @SQL_MSG = 'CON_000A'
        END
        ELSE
        BEGIN
            SET @SQL_MSG = 'ERR_000A'
        END
    END
    ELSE
    BEGIN
        SET @SQL_MSG = 'ERR_003A'
    END
END

RETURN @SQL_MSG
GO