The insert statement conflicted with foreign key constraint

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SQL-Server-2012

Hi, I am using Stored procedure to enter data in the table. Following is my code Of table definition and stored procedure.

CREATE TABLE [StarBazar].[ProductSale] (
    [ProductSaleId] INT           IDENTITY (1, 1) NOT NULL,
    [ProductId]     INT           NOT NULL,
    [C_Id]          INT           NOT NULL,
    [Quantity]      INT           NOT NULL,
    [DateOfSale]    DATETIME2 (7) NOT NULL,
    PRIMARY KEY CLUSTERED ([ProductSaleId] ASC),
    FOREIGN KEY ([ProductId]) REFERENCES [StarBazar].[Products] ([Id]),
    FOREIGN KEY ([C_Id]) REFERENCES [StarBazar].[ClientDetails] ([ClientId])
);


CREATE PROCEDURE [dbo].[usp_InsertProductSale]
	@schemaname nvarchar(20),
	@productid int,
	@clientid int,
	@quantity int
AS
   declare @sql as nvarchar(max)
   set @sql=N'insert into [' +@schemaname + N'].[ProductSale](ProductId,C_Id,Quantity,DateOfSale)
            values(' +CONVERT(NVARCHAR,@productid) + N','+CONVERT(NVARCHAR,@clientid) + N','
			+ CONVERT(NVARCHAR,@quantity)+ N','''+CONVERT(nvarchar,SYSDATETIME()) +N''')'
			print (@sql)
			exec (@sql)
RETURN 0

When I execute the procedure, it gives the following error.
insert into [StarBazar].[ProductSale](ProductId,C_Id,Quantity,DateOfSale)
values(1,1,1,'2015-06-25 10:30:35.0210666')

(1 row(s) affected)

Msg 547, Level 16, State 0, Line 3
The INSERT statement conflicted with the FOREIGN KEY constraint "FK__ProductSa__Clien__56B3DD81". The conflict occurred in database "ReportSystem", table "StarBazar.ClientDetails", column 'ClientId'.
The statement has been terminated.

Help me to solve this.